summaryrefslogtreecommitdiff
path: root/docs/hooks.txt
blob: aca0844adf104b337c41e7067bf482dae61359ee (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
hooks.txt

This document describes how event hooks work in MediaWiki; how to add hooks for
an event; and how to run hooks for an event.

==Glossary==

event
     Something that happens with the wiki. For example: a user logs in. A wiki
     page is saved. A wiki page is deleted. Often there are two events
     associated with a single action: one before the code is run to make the
     event happen, and one after. Each event has a name, preferably in
     CamelCase. For example, 'UserLogin', 'ArticleSave', 'ArticleSaveComplete',
     'ArticleDelete'.

hook
     A clump of code and data that should be run when an event happens. This can
     be either a function and a chunk of data, or an object and a method.

hook function
     The function part of a hook.

==Rationale==

Hooks allow us to decouple optionally-run code from code that is run for
everyone. It allows MediaWiki hackers, third-party developers and local
administrators to define code that will be run at certain points in the mainline
code, and to modify the data run by that mainline code. Hooks can keep mainline
code simple, and make it easier to write extensions. Hooks are a principled
alternative to local patches.

Consider, for example, two options in MediaWiki. One reverses the order of a
title before displaying the article; the other converts the title to all
uppercase letters. Currently, in MediaWiki code, we would handle this as follows
(note: not real code, here):

	function showAnArticle($article) {
		global $wgReverseTitle, $wgCapitalizeTitle;

		if ($wgReverseTitle) {
			wfReverseTitle($article);
		}

		if ($wgCapitalizeTitle) {
			wfCapitalizeTitle($article);
		}

		# code to actually show the article goes here
	}

An extension writer, or a local admin, will often add custom code to the
function -- with or without a global variable. For example, someone wanting
email notification when an article is shown may add:

    function showAnArticle($article) {
        global $wgReverseTitle, $wgCapitalizeTitle, $wgNotifyArticle;

		if ($wgReverseTitle) {
			wfReverseTitle($article);
		}

		if ($wgCapitalizeTitle) {
			wfCapitalizeTitle($article);
		}

		# code to actually show the article goes here

		if ($wgNotifyArticle) {
			wfNotifyArticleShow($article));
		}
	}

Using a hook-running strategy, we can avoid having all this option-specific
stuff in our mainline code. Using hooks, the function becomes:

	function showAnArticle($article) {

		if (wfRunHooks('ArticleShow', array(&$article))) {

			# code to actually show the article goes here

			wfRunHooks('ArticleShowComplete', array(&$article));
		}
	}

We've cleaned up the code here by removing clumps of weird, infrequently used
code and moving them off somewhere else. It's much easier for someone working
with this code to see what's _really_ going on, and make changes or fix bugs.

In addition, we can take all the code that deals with the little-used
title-reversing options (say) and put it in one place. Instead of having little
title-reversing if-blocks spread all over the codebase in showAnArticle,
deleteAnArticle, exportArticle, etc., we can concentrate it all in an extension
file:

	function reverseArticleTitle($article) {
		# ...
	}

	function reverseForExport($article) {
		# ...
	}

The setup function for the extension just has to add its hook functions to the
appropriate events:

	setupTitleReversingExtension() {
		global $wgHooks;

		$wgHooks['ArticleShow'][] = 'reverseArticleTitle';
		$wgHooks['ArticleDelete'][] = 'reverseArticleTitle';
		$wgHooks['ArticleExport'][] = 'reverseForExport';
	}

Having all this code related to the title-reversion option in one place means
that it's easier to read and understand; you don't have to do a grep-find to see
where the $wgReverseTitle variable is used, say.

If the code is well enough isolated, it can even be excluded when not used --
making for some slight savings in memory and load-up performance at runtime.
Admins who want to have all the reversed titles can add:

	require_once('extensions/ReverseTitle.php');

...to their LocalSettings.php file; those of us who don't want or need it can
just leave it out.

The extensions don't even have to be shipped with MediaWiki; they could be
provided by a third-party developer or written by the admin him/herself.

==Writing hooks==

A hook is a chunk of code run at some particular event. It consists of:

  * a function with some optional accompanying data, or
  * an object with a method and some optional accompanying data.

Hooks are registered by adding them to the global $wgHooks array for a given
event. All the following are valid ways to define hooks:

	$wgHooks['EventName'][] = 'someFunction'; # function, no data
	$wgHooks['EventName'][] = array('someFunction', $someData);
	$wgHooks['EventName'][] = array('someFunction'); # weird, but OK

	$wgHooks['EventName'][] = $object; # object only
	$wgHooks['EventName'][] = array($object, 'someMethod');
	$wgHooks['EventName'][] = array($object, 'someMethod', $someData);
	$wgHooks['EventName'][] = array($object); # weird but OK

When an event occurs, the function (or object method) will be called with the
optional data provided as well as event-specific parameters. The above examples
would result in the following code being executed when 'EventName' happened:

	# function, no data
	someFunction($param1, $param2)
	# function with data
	someFunction($someData, $param1, $param2)

	# object only
	$object->onEventName($param1, $param2)
	# object with method
	$object->someMethod($param1, $param2)
	# object with method and data
	$object->someMethod($someData, $param1, $param2)

Note that when an object is the hook, and there's no specified method, the
default method called is 'onEventName'. For different events this would be
different: 'onArticleSave', 'onUserLogin', etc.

The extra data is useful if we want to use the same function or object for
different purposes. For example:

	$wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'TimStarling');
	$wgHooks['ArticleSaveComplete'][] = array('ircNotify', 'brion');

This code would result in ircNotify being run twice when an article is saved:
once for 'TimStarling', and once for 'brion'.

Hooks can return three possible values:

  * true: the hook has operated successfully
  * "some string": an error occurred; processing should stop and the error
                   should be shown to the user
  * false: the hook has successfully done the work necessary and the calling
           function should skip

The last result would be for cases where the hook function replaces the main
functionality. For example, if you wanted to authenticate users to a custom
system (LDAP, another PHP program, whatever), you could do:

	$wgHooks['UserLogin'][] = array('ldapLogin', $ldapServer);

	function ldapLogin($username, $password) {
		# log user into LDAP
		return false;
	}

Returning false makes less sense for events where the action is complete, and
will normally be ignored.

Note that none of the examples made use of create_function() as a way to
attach a function to a hook. This is known to cause problems (notably with
Special:Version), and should be avoided when at all possible.

==Using hooks==

A calling function or method uses the wfRunHooks() function to run the hooks
related to a particular event, like so:

	class Article {
		# ...
		function protect() {
			global $wgUser;
			if (wfRunHooks('ArticleProtect', array(&$this, &$wgUser))) {
				# protect the article
				wfRunHooks('ArticleProtectComplete', array(&$this, &$wgUser));
			}
		}
	}

wfRunHooks() returns true if the calling function should continue processing
(the hooks ran OK, or there are no hooks to run), or false if it shouldn't (an
error occurred, or one of the hooks handled the action already). Checking the
return value matters more for "before" hooks than for "complete" hooks.

Note that hook parameters are passed in an array; this is a necessary
inconvenience to make it possible to pass reference values (that can be changed)
into the hook code. Also note that earlier versions of wfRunHooks took a
variable number of arguments; the array() calling protocol came about after
MediaWiki 1.4rc1.

==Events and parameters==

This is a list of known events and parameters; please add to it if you're going
to add events to the MediaWiki code.

'AbortAutoAccount': Return false to cancel automated local account creation, where normally authentication against an external auth plugin would be creating a local account.
$user: the User object about to be created (read-only, incomplete)
&$abortMsg: out parameter: name of error message to be displayed to user

'AbortAutoblock': Return false to cancel an autoblock.
$autoblockip: The IP going to be autoblocked.
$block: The block from which the autoblock is coming.

'AbortDiffCache': Can be used to cancel the caching of a diff
&$diffEngine: DifferenceEngine object

'AbortLogin': Return false to cancel account login.
$user: the User object being authenticated against
$password: the password being submitted, not yet checked for validity
&$retval: a LoginForm class constant to return from authenticateUserData();
          default is LoginForm::ABORTED. Note that the client may be using
          a machine API rather than the HTML user interface.
&$msg: the message identifier for abort reason (new in 1.18, not available before 1.18)

'AbortMove': allows to abort moving an article (title)
$old: old title
$nt: new title
$user: user who is doing the move
$err: error message
$reason: the reason for the move (added in 1.13)

'AbortNewAccount': Return false to cancel explicit account creation.
$user: the User object about to be created (read-only, incomplete)
&$msg: out parameter: name of error message to display on abort

'ActionBeforeFormDisplay': before executing the HTMLForm object
$name: name of the action
&$form: HTMLForm object
$article: Article object

'ActionModifyFormFields': before creating an HTMLForm object for a page action;
	allows to change the fields on the form that will be generated
$name: name of the action
&$fields: HTMLForm descriptor array
$article: Article object

'AddNewAccount': after a user account is created
$user: the User object that was created. (Parameter added in 1.7)
$byEmail: true when account was created "by email" (added in 1.12)

'AfterImportPage': When a page import is completed
$title: Title under which the revisions were imported
$origTitle: Title provided by the XML file
$revCount: Number of revisions in the XML file
$sRevCount: Number of sucessfully imported revisions
$pageInfo: associative array of page information

'AjaxAddScript': Called in output page just before the initialisation
of the javascript ajax engine. The hook is only called when ajax
is enabled ( $wgUseAjax = true; ).

'AlternateEdit': before checking if an user can edit a page and
before showing the edit form ( EditPage::edit() ). This is triggered
on &action=edit.
$EditPage: the EditPage object

'APIAfterExecute': after calling the execute() method of an API module.
Use this to extend core API modules.
&$module: Module object

'APIEditBeforeSave': before saving a page with api.php?action=edit,
after processing request parameters. Return false to let the request
fail, returning an error message or an <edit result="Failure"> tag
if $resultArr was filled.
$EditPage : the EditPage object
$text : the new text of the article (has yet to be saved)
&$resultArr : data in this array will be added to the API result

'APIGetAllowedParams': use this hook to modify a module's parameters.
&$module: Module object
&$params: Array of parameters

'APIGetParamDescription': use this hook to modify a module's parameter
descriptions.
&$module: Module object
&$desc: Array of parameter descriptions

'APIQueryAfterExecute': after calling the execute() method of an
action=query submodule. Use this to extend core API modules.
&$module: Module object

'APIQueryGeneratorAfterExecute': after calling the executeGenerator()
method of an action=query submodule. Use this to extend core API modules.
&$module: Module object
&$resultPageSet: ApiPageSet object

'APIQueryInfoTokens': use this hook to add custom tokens to prop=info.
Every token has an action, which will be used in the intoken parameter
and in the output (actiontoken="..."), and a callback function which
should return the token, or false if the user isn't allowed to obtain
it. The prototype of the callback function is func($pageid, $title)
where $pageid is the page ID of the page the token is requested for
and $title is the associated Title object. In the hook, just add
your callback to the $tokenFunctions array and return true (returning
false makes no sense)
$tokenFunctions: array(action => callback)

'APIQueryRevisionsTokens': use this hook to add custom tokens to prop=revisions.
Every token has an action, which will be used in the rvtoken parameter
and in the output (actiontoken="..."), and a callback function which
should return the token, or false if the user isn't allowed to obtain
it. The prototype of the callback function is func($pageid, $title, $rev)
where $pageid is the page ID of the page associated to the revision the
token is requested for, $title the associated Title object and $rev the
associated Revision object. In the hook, just add your callback to the
$tokenFunctions array and return true (returning false makes no sense)
$tokenFunctions: array(action => callback)

'APIQueryRecentChangesTokens': use this hook to add custom tokens to
list=recentchanges.
Every token has an action, which will be used in the rctoken parameter
and in the output (actiontoken="..."), and a callback function which
should return the token, or false if the user isn't allowed to obtain
it. The prototype of the callback function is func($pageid, $title, $rc)
where $pageid is the page ID of the page associated to the revision the
token is requested for, $title the associated Title object and $rc the
associated RecentChange object. In the hook, just add your callback to the
$tokenFunctions array and return true (returning false makes no sense)
$tokenFunctions: array(action => callback)

'APIQuerySiteInfoGeneralInfo': use this hook to add extra information to
the sites general information.
$module: the current ApiQuerySiteInfo module
&$results: array of results, add things here

'APIQueryUsersTokens': use this hook to add custom token to list=users.
Every token has an action, which will be used in the ustoken parameter
and in the output (actiontoken="..."), and a callback function which
should return the token, or false if the user isn't allowed to obtain
it. The prototype of the callback function is func($user) where $user
is the User object. In the hook, just add your callback to the
$tokenFunctions array and return true (returning false makes no sense)
$tokenFunctions: array(action => callback)

'ApiRsdServiceApis': Add or remove APIs from the RSD services list.
Each service should have its own entry in the $apis array and have a
unique name, passed as key for the array that represents the service data.
In this data array, the key-value-pair identified by the apiLink key is 
required.
&$apis: array of services

'ArticleAfterFetchContent': after fetching content of an article from
the database
$article: the article (object) being loaded from the database
$content: the content (string) of the article

'ArticleConfirmDelete': before writing the confirmation form for article
	deletion
$article: the article (object) being deleted
$output: the OutputPage object ($wgOut)
&$reason: the reason (string) the article is being deleted

'ArticleContentOnDiff': before showing the article content below a diff.
Use this to change the content in this area or how it is loaded.
 $diffEngine: the DifferenceEngine
 $output: the OutputPage object ($wgOut)

'ArticleDelete': before an article is deleted
$article: the article (object) being deleted
$user: the user (object) deleting the article
$reason: the reason (string) the article is being deleted
$error: if the deletion was prohibited, the (raw HTML) error message to display
  (added in 1.13)

'ArticleDeleteComplete': after an article is deleted
$article: the article that was deleted
$user: the user that deleted the article
$reason: the reason the article was deleted
$id: id of the article that was deleted

'ArticleEditUpdateNewTalk': before updating user_newtalk when a user talk page
was changed
$article: article (object) of the user talk page

'ArticleEditUpdates': when edit updates (mainly link tracking) are made when an
article has been changed
$article: the article (object)
$editInfo: data holder that includes the parser output ($editInfo->output) for
that page after the change
$changed: bool for if the page was changed

'ArticleEditUpdatesDeleteFromRecentchanges': before deleting old entries from
recentchanges table, return false to not delete old entries
$article: article (object) being modified

'ArticleFromTitle': when creating an article object from a title object using
Wiki::articleFromTitle()
$title: title (object) used to create the article object
$article: article (object) that will be returned

'ArticleInsertComplete': After a new article is created
$article: Article created
$user: User creating the article
$text: New content
$summary: Edit summary/comment
$isMinor: Whether or not the edit was marked as minor
$isWatch: (No longer used)
$section: (No longer used)
$flags: Flags passed to Article::doEdit()
$revision: New Revision of the article

'ArticleMergeComplete': after merging to article using Special:Mergehistory
$targetTitle: target title (object)
$destTitle: destination title (object)

'ArticlePageDataAfter': after loading data of an article from the database
$article: article (object) whose data were loaded
$row: row (object) returned from the database server

'ArticlePageDataBefore': before loading data of an article from the database
$article: article (object) that data will be loaded
$fields: fileds (array) to load from the database

'ArticlePrepareTextForEdit': called when preparing text to be saved
$article: the article being saved
$popts: parser options to be used for pre-save transformation

'ArticleProtect': before an article is protected
$article: the article being protected
$user: the user doing the protection
$protect: boolean whether this is a protect or an unprotect
$reason: Reason for protect
$moveonly: boolean whether this is for move only or not

'ArticleProtectComplete': after an article is protected
$article: the article that was protected
$user: the user who did the protection
$protect: boolean whether it was a protect or an unprotect
$reason: Reason for protect
$moveonly: boolean whether it was for move only or not

'ArticlePurge': before executing "&action=purge"
$article: article (object) to purge

'ArticleRevisionVisibilitySet': called when changing visibility of one or more
revision of an article
&$title: title object of the article

'ArticleRevisionUndeleted': after an article revision is restored
$title: the article title
$revision: the revision
$oldPageID: the page ID of the revision when archived (may be null)

'ArticleRollbackComplete': after an article rollback is completed
$article: the article that was edited
$user: the user who did the rollback
$revision: the revision the page was reverted back to
$current: the reverted revision

'ArticleSave': before an article is saved
$article: the article (object) being saved
$user: the user (object) saving the article
$text: the new article text
$summary: the article summary (comment)
$isminor: minor flag
$iswatch: watch flag
$section: section #

'ArticleSaveComplete': After an article has been updated
$article: Article modified
$user: User performing the modification
$text: New content
$summary: Edit summary/comment
$isMinor: Whether or not the edit was marked as minor
$isWatch: (No longer used)
$section: (No longer used)
$flags: Flags passed to Article::doEdit()
$revision: New Revision of the article
$baseRevId: the rev ID (or false) this edit was based on

'ArticleUndelete': When one or more revisions of an article are restored
$title: Title corresponding to the article restored
$create: Whether or not the restoration caused the page to be created
(i.e. it didn't exist before)
$comment: The comment associated with the undeletion.

'ArticleUpdateBeforeRedirect': After a page is updated (usually on save),
before the user is redirected back to the page
&$article: the article
&$sectionanchor: The section anchor link (e.g. "#overview" )
&$extraq: Extra query parameters which can be added via hooked functions

'ArticleViewFooter': After showing the footer section of an ordinary page view
$article: Article object

'ArticleViewHeader': Before the parser cache is about to be tried for article
viewing.
&$article: the article
&$pcache: whether to try the parser cache or not
&$outputDone: whether the output for this page finished or not

'ArticleViewRedirect': before setting "Redirected from ..." subtitle when
follwed an redirect
$article: target article (object)

'AuthPluginAutoCreate': Called when creating a local account for an user logged
in from an external authentication method
$user: User object created locally

'AuthPluginSetup': update or replace authentication plugin object ($wgAuth)
Gives a chance for an extension to set it programattically to a variable class.
&$auth: the $wgAuth object, probably a stub

'AutopromoteCondition': check autopromote condition for user.
$type: condition type
$args: arguments
$user: user
$result: result of checking autopromote condition

'BadImage': When checking against the bad image list
$name: Image name being checked
&$bad: Whether or not the image is "bad"

Change $bad and return false to override. If an image is "bad", it is not
rendered inline in wiki pages or galleries in category pages.

'BeforeInitialize': before anything is initialized in performRequestForTitle()
&$title: Title being used for request
&$article: The associated Article object
&$output: OutputPage object
&$user: User
$request: WebRequest object
$mediaWiki: Mediawiki object

'BeforePageDisplay': Prior to outputting a page
&$out: OutputPage object
&$skin: Skin object

'BeforePageRedirect': Prior to sending an HTTP redirect. Gives a chance to
override how the redirect is output by modifying, or by returning false and
taking over the output.
$out: OutputPage object
&$redirect: URL, modifiable
&$code: HTTP code (eg '301' or '302'), modifiable

'BeforeParserFetchFileAndTitle': before an image is rendered by Parser
$parser: Parser object
$nt: the image title
&$time: the image timestamp (use '0' to force a broken thumbnail)
&$sha1: image base 36 sha1 (used to specify the file, $nt will be ignored if this is set)
&$descQuery: query string to add to thumbnail URL

'BeforeParserFetchTemplateAndtitle': before a template is fetched by Parser
$parser: Parser object
$title: title of the template
&$skip: skip this template and link it?
&$id: the id of the revision being parsed

'BeforeParserrenderImageGallery': before an image gallery is rendered by Parser
&$parser: Parser object
&$ig: ImageGallery object

'BeforeWelcomeCreation': before the welcomecreation message is displayed to a newly created user 
&$welcome_creation_msg: MediaWiki message name to display on the welcome screen to a newly created user account
&$injected_html: Any HTML to inject after the "logged in" message of a newly created user account 

'BitmapHandlerTransform': before a file is transformed, gives extension the 
possibility to transform it themselves
$handler: BitmapHandler 
$image: File
&$scalerParams: Array with scaler parameters 
&$mto: null, set to a MediaTransformOutput

'PerformRetroactiveAutoblock': called before a retroactive autoblock is applied to a user
$block: Block object (which is set to be autoblocking)
&$blockIds: Array of block IDs of the autoblock

'BlockIp': before an IP address or user is blocked
$block: the Block object about to be saved
$user: the user _doing_ the block (not the one being blocked)

'BlockIpComplete': after an IP address or user is blocked
$block: the Block object that was saved
$user: the user who did the block (not the one being blocked)

'BookInformation': Before information output on Special:Booksources
$isbn: ISBN to show information for
$output: OutputPage object in use

'CanonicalNamespaces': For extensions adding their own namespaces or altering the defaults
&$namespaces: Array of namespace numbers with corresponding canonical names
 
'CategoryPageView': before viewing a categorypage in CategoryPage::view
$catpage: CategoryPage instance

'ChangesListInsertArticleLink': Override or augment link to article in RC list.
&$changesList: ChangesList instance.
&$articlelink: HTML of link to article (already filled-in).
&$s:           HTML of row that is being constructed.
&$rc:          RecentChange instance.
$unpatrolled:  Whether or not we are showing unpatrolled changes.
$watched:      Whether or not the change is watched by the user.

'Collation::factory': Called if $wgCategoryCollation is an unknown collation
$collationName: Name of the collation in question
&$collationObject: Null. Replace with a subclass of the Collation class that implements
the collation given in $collationName.

'ConfirmEmailComplete': Called after a user's email has been confirmed successfully
$user: user (object) whose email is being confirmed

'ContribsPager::getQueryInfo': Before the contributions query is about to run
&$pager: Pager object for contributions
&$queryInfo: The query for the contribs Pager

'ContributionsLineEnding': Called before a contributions HTML line is finished
$page: SpecialPage object for contributions
$ret: the HTML line
$row: the DB row for this line

'ContributionsToolLinks': Change tool links above Special:Contributions
$id: User identifier
$title: User page title
&$tools: Array of tool links

'CustomEditor': When invoking the page editor
$article: Article being edited
$user: User performing the edit

Return true to allow the normal editor to be used, or false
if implementing a custom editor, e.g. for a special namespace,
etc.

'DatabaseOraclePostInit': Called after initialising an Oracle database
&$db: the DatabaseOracle object

'Debug': called when outputting a debug log line via wfDebug() or wfDebugLog()
$text: plaintext string to be output
$group: null or a string naming a logging group (as defined in $wgDebugLogGroups)

'NewDifferenceEngine': Called when a new DifferenceEngine object is made
$title: the diff page title (nullable)
&$oldId: the actual old Id to use in the diff
&$newId: the actual new Id to use in the diff (0 means current)
$old: the ?old= param value from the url
$new: the ?new= param value from the url

'DiffViewHeader': called before diff display
$diff: DifferenceEngine object that's calling
$oldRev: Revision object of the "old" revision (may be null/invalid)
$newRev: Revision object of the "new" revision

'DisplayOldSubtitle': before creating subtitle when browsing old versions of
an article
$article: article (object) being viewed
$oldid: oldid (int) being viewed

'DoEditSectionLink': Override the HTML generated for section edit links
$skin: Skin object rendering the UI
$title: Title object for the title being linked to (may not be the same as
  $wgTitle, if the section is included from a template)
$section: The designation of the section being pointed to, to be included in
  the link, like "&section=$section"
$tooltip: The default tooltip.  Escape with htmlspecialchars() before using.
  By default, this is wrapped in the 'editsectionhint' message.
&$result: The HTML to return, prefilled with the default plus whatever other
  changes earlier hooks have made
$lang: The language code to use for the link in the wfMsg* functions

'EditFilter': Perform checks on an edit
$editor: Edit form (see includes/EditPage.php)
$text: Contents of the edit box
$section: Section being edited
&$error: Error message to return
$summary: Edit summary for page

'EditFilterMerged': Post-section-merge edit filter
$editor: EditPage instance (object)
$text: content of the edit box
&$error: error message to return
$summary: Edit summary for page

'EditFormPreloadText': Allows population of the edit form when creating
new pages
&$text: Text to preload with
&$title: Title object representing the page being created

'EditFormInitialText': Allows modifying the edit form when editing existing
pages
$editPage: EditPage	object

'EditPage::attemptSave': called before an article is
saved, that is before Article::doEdit() is called
$editpage_Obj: the current EditPage object

'EditPage::importFormData': allow extensions to read additional data
posted in the form
$editpage: EditPage instance 
$request: Webrequest
return value is ignored (should always return true)

'EditPage::showEditForm:fields': allows injection of form field into edit form
&$editor: the EditPage instance for reference
&$out: an OutputPage instance to write to
return value is ignored (should always return true)

'EditPage::showEditForm:initial': before showing the edit form
$editor: EditPage instance (object)

Return false to halt editing; you'll need to handle error messages, etc.
yourself. Alternatively, modifying $error and returning true will cause the
contents of $error to be echoed at the top of the edit form as wikitext.
Return true without altering $error to allow the edit to proceed.

'EditPageBeforeConflictDiff': allows modifying the EditPage object and output
when there's an edit conflict.  Return false to halt normal diff output; in
this case you're responsible for computing and outputting the entire "conflict"
part, i.e., the "difference between revisions" and "your text" headers and
sections.
&$editor: EditPage instance
&$out: OutputPage instance

'EditPageBeforeEditButtons':  allows modifying the edit buttons below the
textarea in the edit form
&$editpage: The current EditPage object
&$buttons: Array of edit buttons "Save", "Preview", "Live", and "Diff"
&$tabindex: HTML tabindex of the last edit check/button

'EditPageBeforeEditChecks':  allows modifying the edit checks below the
textarea in the edit form
&$editpage: The current EditPage object
&$checks: Array of edit checks like "watch this page"/"minor edit"
&$tabindex: HTML tabindex of the last edit check/button

'EditPageBeforeEditToolbar': allows modifying the edit toolbar above the
textarea in the edit form
&$toolbar: The toolbar HTMl

'EditPageCopyrightWarning': Allow for site and per-namespace customization of contribution/copyright notice.
$title: title of page being edited
&$msg: localization message name, overridable. Default is either 'copyrightwarning' or 'copyrightwarning2'

'EditPageGetDiffText': Allow modifying the wikitext that will be used in
"Show changes"
$editPage: EditPage object
&$newtext: wikitext that will be used as "your version"

'EditPageGetPreviewText': Allow modifying the wikitext that will be previewed
$editPage: EditPage object
&$toparse: wikitext that will be parsed

'EditPageNoSuchSection': When a section edit request is given for an non-existent section
&$editpage: The current EditPage object
&$res: the HTML of the error text

'EditPageTosSummary':  Give a chance for site and per-namespace customizations
of terms of service summary link that might exist separately from the copyright
notice.
$title: title of page being edited
&$msg: localization message name, overridable. Default is 'editpage-tos-summary'

'EditSectionLink': Do not use, use DoEditSectionLink instead.
$skin: Skin rendering the UI
$title: Title being linked to
$section: Section to link to
$link: Default link
&$result: Result (alter this to override the generated links)
$lang: The language code to use for the link in the wfMsg* functions

'EmailConfirmed': When checking that the user's email address is "confirmed"
$user: User being checked
$confirmed: Whether or not the email address is confirmed
This runs before the other checks, such as anonymity and the real check; return
true to allow those checks to occur, and false if checking is done.

'EmailUser': before sending email from one user to another
$to: address of receiving user
$from: address of sending user
$subject: subject of the mail
$text: text of the mail

'EmailUserCC': before sending the copy of the email to the author
$to: address of receiving user
$from: address of sending user
$subject: subject of the mail
$text: text of the mail

'EmailUserComplete': after sending email from one user to another
$to: address of receiving user
$from: address of sending user
$subject: subject of the mail
$text: text of the mail

'EmailUserForm': after building the email user form object
$form: HTMLForm object

'EmailUserPermissionsErrors': to retrieve permissions errors for emailing a user.
$user: The user who is trying to email another user.
$editToken: The user's edit token.
&$hookErr: Out-param for the error. Passed as the parameters to OutputPage::showErrorPage.

'ExtensionTypes': called when generating the extensions credits, use this to change the tables headers
&$extTypes: associative array of extensions types

'FetchChangesList': When fetching the ChangesList derivative for
a particular user
$user: User the list is being fetched for
&$skin: Skin object to be used with the list
&$list: List object (defaults to NULL, change it to an object
	instance and return false override the list derivative used)

'FileDeleteComplete': When a file is deleted
$file: reference to the deleted file
$oldimage: in case of the deletion of an old image, the name of the old file
$article: in case all revisions of the file are deleted a reference to the
	article associated with the file.
$user: user who performed the deletion
$reason: reason

'FileUpload': When a file upload occurs
$file : Image object representing the file that was uploaded
$reupload : Boolean indicating if there was a previously another image there or not (since 1.17)
$hasDescription : Boolean indicating that there was already a description page and a new one from the comment wasn't created (since 1.17)

'FileUndeleteComplete': When a file is undeleted
$title: title object to the file
$fileVersions: array of undeleted versions. Empty if all versions were restored
$user: user who performed the undeletion
$reason: reason

'GetAutoPromoteGroups': When determining which autopromote groups a user
is entitled to be in.
&$user: user to promote.
&$promote: groups that will be added.

'GetBlockedStatus': after loading blocking status of an user from the database
$user: user (object) being checked

'GetCacheVaryCookies': get cookies that should vary cache options
$out: OutputPage object
&$cookies: array of cookies name, add a value to it if you want to add a cookie
	that have to vary cache options

'GetCanonicalURL': modify fully-qualified URLs used for IRC and e-mail notifications
$title: Title object of page
$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getCanonicalURL()
$variant: variant passed to Title::getCanonicalURL()

'GetDefaultSortkey': Override the default sortkey for a page.
$title: Title object that we need to get a sortkey for
&$sortkey: Sortkey to use.

'GetFullURL': modify fully-qualified URLs used in redirects/export/offsite data
$title: Title object of page
$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getFullURL()
$variant: variant passed to Title::getFullURL()

'GetInternalURL': modify fully-qualified URLs used for squid cache purging
$title: Title object of page
$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getInternalURL()
$variant: variant passed to Title::getFullURL()

'GetIP': modify the ip of the current user (called only once)
&$ip: string holding the ip as determined so far

'GetLinkColours': modify the CSS class of an array of page links
$linkcolour_ids: array of prefixed DB keys of the pages linked to,
	indexed by page_id.
&$colours: (output) array of CSS classes, indexed by prefixed DB keys

'GetLocalURL': modify local URLs as output into page links
$title: Title object of page
$url: string value as output (out parameter, can modify)
$query: query options passed to Title::getLocalURL()
$variant: variant passed to Title::getLocalURL()

'GetMetadataVersion': modify the image metadata version currently in use. This is
	used when requesting image metadata from a ForiegnApiRepo. Media handlers
	that need to have versioned metadata should add an element to the end of
	the version array of the form 'handler_name=version'. Most media handlers
	won't need to do this unless they broke backwards compatibility with a
	previous version of the media handler metadata output. 
&$version: Array of version strings

'GetPreferences': modify user preferences
$user: User whose preferences are being modified.
&$preferences: Preferences description array, to be fed to an HTMLForm object

'getUserPermissionsErrors': Add a permissions error when permissions errors are
	checked for.  Use instead of userCan for most cases. Return false if the
	user can't do it, and populate $result with the reason in the form of
	array( messagename, param1, param2, ... ).  For consistency, error messages
	should be plain text with no special coloring, bolding, etc. to show that
	they're errors; presenting them properly to the user as errors is done by
	the caller.
$title: Title object being checked against
$user : Current user object
$action: Action being checked
$result: User permissions error to add. If none, return true.

'getUserPermissionsErrorsExpensive': Absolutely the same, but is called only
	if expensive checks are enabled.

'ImageBeforeProduceHTML': Called before producing the HTML created by a wiki
	image insertion.  You can skip the default logic entirely by returning
	false, or just modify a	few things using call-by-reference.
&$skin: Skin object
&$title: Title object of the image
&$file: File object, or false if it doesn't exist
&$frameParams: Various parameters with special meanings; see documentation in
	includes/Linker.php for Linker::makeImageLink2
&$handlerParams: Various parameters with special meanings; see documentation in
	includes/Linker.php for Linker::makeImageLink2
&$time: Timestamp of file in 'YYYYMMDDHHIISS' string form, or false for current
&$res: Final HTML output, used if you return false


'ImageOpenShowImageInlineBefore': Call potential extension just before showing
	the image on an image page
$imagePage: ImagePage object ($this)
$output: $wgOut

'ImagePageAfterImageLinks': called after the image links section on an image 
	page is built
$imagePage: ImagePage object ($this)
&$html: HTML for the hook to add

'ImagePageFileHistoryLine': called when a file history line is contructed
$file: the file
$line: the HTML of the history line
$css: the line CSS class

'ImagePageFindFile': called when fetching the file associated with an image page
$page: ImagePage object
&$file: File object
&$displayFile: displayed File object

'ImagePageShowTOC': called when the file toc on an image page is generated
$page: ImagePage object
&$toc: Array of <li> strings

'ImgAuthBeforeStream': executed before file is streamed to user, but only when
	using img_auth.php
&$title: the Title object of the file as it would appear for the upload page
&$path: the original file and path name when img_auth was invoked by the the web
	server
&$name: the name only component of the file
&$result: The location to pass back results of the hook routine (only used if
	failed)
	$result[0]=The index of the header message
	$result[1]=The index of the body text message
	$result[2 through n]=Parameters passed to body text message. Please note the
	header message cannot receive/use parameters.

'ImportHandleLogItemXMLTag': When parsing a XML tag in a log item
$reader: XMLReader object
$logInfo: Array of information
Return false to stop further processing of the tag

'ImportHandlePageXMLTag': When parsing a XML tag in a page
$reader: XMLReader object
$pageInfo: Array of information
Return false to stop further processing of the tag

'ImportHandleRevisionXMLTag': When parsing a XML tag in a page revision
$reader: XMLReader object
$revInfo: Array of information
Return false to stop further processing of the tag

'ImportHandleToplevelXMLTag': When parsing a top level XML tag
$reader: XMLReader object
Return false to stop further processing of the tag

'ImportHandleUploadXMLTag': When parsing a XML tag in a file upload
$reader: XMLReader object
$revisionInfo: Array of information
Return false to stop further processing of the tag

'InitializeArticleMaybeRedirect': MediaWiki check to see if title is a redirect
$title: Title object ($wgTitle)
$request: WebRequest
$ignoreRedirect: boolean to skip redirect check
$target: Title/string of redirect target
$article: Article object

'InterwikiLoadPrefix': When resolving if a given prefix is an interwiki or not.
Return true without providing an interwiki to continue interwiki search.
$prefix: interwiki prefix we are looking for.
&$iwData: output array describing the interwiki with keys iw_url, iw_local, 
  iw_trans and optionally iw_api and iw_wikiid.

'InternalParseBeforeLinks': during Parser's internalParse method before links
but after noinclude/includeonly/onlyinclude and other processing.
&$parser: Parser object
&$text: string containing partially parsed text
&$stripState: Parser's internal StripState object

'InvalidateEmailComplete': Called after a user's email has been invalidated successfully
$user: user (object) whose email is being invalidated

'IRCLineURL': When constructing the URL to use in an IRC notification.
Callee may modify $url and $query, URL will be constructed as $url . $query
&$url: URL to index.php
&$query: Query string

'IsFileCacheable': Override the result of Article::isFileCacheable() (if true)
$article: article (object) being checked

'IsTrustedProxy': Override the result of wfIsTrustedProxy()
$ip: IP being check
$result: Change this value to override the result of wfIsTrustedProxy()

'isValidEmailAddr': Override the result of User::isValidEmailAddr(), for ins-
tance to return false if the domain name doesn't match your organization
$addr: The e-mail address entered by the user
&$result: Set this and return false to override the internal checks

'isValidPassword': Override the result of User::isValidPassword()
$password: The password entered by the user
&$result: Set this and return false to override the internal checks
$user: User the password is being validated for

'LanguageGetMagic': DEPRECATED, use $magicWords in a file listed in 
$wgExtensionMessagesFiles instead. 
Use this to define synonyms of magic words depending of the language
$magicExtensions: associative array of magic words synonyms
$lang: laguage code (string)

'LanguageGetSpecialPageAliases': DEPRECATED, use $specialPageAliases in a file
listed in $wgExtensionMessagesFiles instead.
Use to define aliases of special pages names depending of the language
$specialPageAliases: associative array of magic words synonyms
$lang: laguage code (string)

'LanguageGetTranslatedLanguageNames': Provide translated language names.
&$names: array of language code => language name
$code language of the preferred translations

'LinkBegin': Used when generating internal and interwiki links in
Linker::link(), before processing starts.  Return false to skip default proces-
sing and return $ret.  See documentation for Linker::link() for details on the
expected meanings of parameters.
$skin: the Skin object
$target: the Title that the link is pointing to
&$html: the contents that the <a> tag should have (raw HTML); null means "de-
	fault"
&$customAttribs: the HTML attributes that the <a> tag should have, in associa-
	tive array form, with keys and values unescaped.  Should be merged with de-
	fault values, with a value of false meaning to suppress the attribute.
&$query: the query string to add to the generated URL (the bit after the "?"),
	in associative array form, with keys and values unescaped.
&$options: array of options.  Can include 'known', 'broken', 'noclasses'.
&$ret: the value to return if your hook returns false.

'LinkEnd': Used when generating internal and interwiki links in Linker::link(),
just before the function returns a value.  If you return true, an <a> element
with HTML attributes $attribs and contents $html will be returned.  If you re-
turn false, $ret will be returned.
$skin: the Skin object
$target: the Title object that the link is pointing to
$options: the options.  Will always include either 'known' or 'broken', and may
	include 'noclasses'.
&$html: the final (raw HTML) contents of the <a> tag, after processing.
&$attribs: the final HTML attributes of the <a> tag, after processing, in asso-
	ciative array form.
&$ret: the value to return if your hook returns false.

'LinkerMakeExternalImage': At the end of Linker::makeExternalImage() just
before the return
&$url: the image url
&$alt: the image's alt text
&$img: the new image HTML (if returning false)

'LinkerMakeExternalLink': At the end of Linker::makeExternalLink() just
before the return
&$url: the link url
&$text: the link text
&$link: the new link HTML (if returning false)
&$attribs: the attributes to be applied.
$linkType: The external link type

'LinksUpdate': At the beginning of LinksUpdate::doUpdate() just before the
actual update
&$linksUpdate: the LinksUpdate object

'LinksUpdateComplete': At the end of LinksUpdate::doUpdate() when updating has
completed
&$linksUpdate: the LinksUpdate object

'LinksUpdateConstructed': At the end of LinksUpdate() is contruction.
&$linksUpdate: the LinksUpdate object

'ListDefinedTags': When trying to find all defined tags.
&$tags: The list of tags.

'LoadExtensionSchemaUpdates': called during database installation and updates
&updater: A DatabaseUpdater subclass

'LocalFile::getHistory': called before file history query performed
$file: the file
$tables: tables
$fields: select fields
$conds: conditions
$opts: query options
$join_conds: JOIN conditions

'LocalisationCacheRecache': Called when loading the localisation data into cache
$cache: The LocalisationCache object
$code: language code
&$alldata: The localisation data from core and extensions

'LoginAuthenticateAudit': a login attempt for a valid user account either
succeeded or failed. No return data is accepted; this hook is for auditing only.
$user: the User object being authenticated against
$password: the password being submitted and found wanting
$retval: a LoginForm class constant with authenticateUserData() return
	value (SUCCESS, WRONG_PASS, etc)

'LogLine': Processes a single log entry on Special:Log
$log_type: string for the type of log entry (e.g. 'move'). Corresponds to
	logging.log_type database field.
$log_action: string for the type of log action (e.g. 'delete', 'block',
	'create2'). Corresponds to logging.log_action database field.
$title: Title object that corresponds to logging.log_namespace and
	logging.log_title database fields.
$paramArray: Array of parameters that corresponds to logging.log_params field.
	Note that only $paramArray[0] appears to contain anything.
&$comment: string that corresponds to logging.log_comment database field, and
	which is displayed in the UI.
&$revert: string that is displayed in the UI, similar to $comment.
$time: timestamp of the log entry (added in 1.12)

'MaintenanceRefreshLinksInit': before executing the refreshLinks.php maintenance script
$refreshLinks: RefreshLinks object

'MagicWordMagicWords': When defining new magic word.
DEPRECATED: use $magicWords in a file listed in 
$wgExtensionMessagesFiles instead.
$magicWords: array of strings

'MagicWordwgVariableIDs': When definig new magic words IDs.
$variableIDs: array of strings

'MakeGlobalVariablesScript': called right before Skin::makeVariablesScript
is executed. Ideally, this hook should only be used to add variables that
depend on the current page/request; static configuration should be added
through ResourceLoaderGetConfigVars instead.
&$vars: variable (or multiple variables) to be added into the output
	of Skin::makeVariablesScript

'MarkPatrolled': before an edit is marked patrolled
$rcid: ID of the revision to be marked patrolled
$user: the user (object) marking the revision as patrolled
$wcOnlySysopsCanPatrol: config setting indicating whether the user
	needs to be a sysop in order to mark an edit patrolled

'MarkPatrolledComplete': after an edit is marked patrolled
$rcid: ID of the revision marked as patrolled
$user: user (object) who marked the edit patrolled
$wcOnlySysopsCanPatrol: config setting indicating whether the user
	must be a sysop to patrol the edit

'MediaWikiPerformAction': Override MediaWiki::performAction().
Use this to do something completely different, after the basic
globals have been set up, but before ordinary actions take place.
$output: $wgOut
$article: $wgArticle
$title: $wgTitle
$user: $wgUser
$request: $wgRequest
$mediaWiki: The $mediawiki object

'MessagesPreLoad': When loading a message from the database
$title: title of the message (string)
$message: value (string), change it to the message you want to define

'MessageCacheReplace': When a message page is changed.
Useful for updating caches.
$title: name of the page changed.
$text: new contents of the page.

'ModifyExportQuery': Modify the query used by the exporter.
$db: The database object to be queried.
&$tables: Tables in the query.
&$conds: Conditions in the query.
&$opts: Options for the query.
&$join_conds: Join conditions for the query.

'MonoBookTemplateToolboxEnd': Called by Monobook skin after toolbox links have
been rendered (useful for adding more)
Note: this is only run for the Monobook skin. This hook is deprecated and
may be removed in the future. To add items to the toolbox you should use 
the SkinTemplateToolboxEnd hook instead, which works for all 
"SkinTemplate"-type skins.
$tools: array of tools

'BaseTemplateToolbox': Called by BaseTemplate when building the $toolbox array
and returning it for the skin to output. You can add items to the toolbox while
still letting the skin make final decisions on skin-specific markup conventions
using this hook.
&$sk: The BaseTemplate base skin template
&$toolbox: An array of toolbox items, see BaseTemplate::getToolbox and
	BaseTemplate::makeListItem for details on the format of individual
	items inside of this array

'NewRevisionFromEditComplete': called when a revision was inserted
due to an edit
$article: the article edited
$rev: the new revision
$baseID: the revision ID this was based off, if any
$user: the editing user

'NormalizeMessageKey': Called before the software gets the text of a message
(stuff in the MediaWiki: namespace), useful for changing WHAT message gets
displayed
&$key: the message being looked up. Change this to something else to change
	what message gets displayed (string)
&$useDB: whether or not to look up the message in the database (bool)
&$langCode: the language code to get the message for (string) - or -
	whether to use the content language (true) or site language (false) (bool)
&$transform: whether or not to expand variables and templates
	in the message (bool)

'OldChangesListRecentChangesLine': Customize entire Recent Changes line.
&$changeslist: The OldChangesList instance.
&$s: HTML of the form "<li>...</li>" containing one RC entry.
&$rc: The RecentChange object.

'OpenSearchUrls': Called when constructing the OpenSearch description XML.
Hooks can alter or append to the array of URLs for search & suggestion formats.
&$urls: array of associative arrays with Url element attributes

'OtherBlockLogLink': Get links to the block log from extensions which blocks
	users and/or IP addresses too
$otherBlockLink: An array with links to other block logs
$ip: The requested IP address or username

'OutputPageBeforeHTML': a page has been processed by the parser and
the resulting HTML is about to be displayed.
$parserOutput: the parserOutput (object) that corresponds to the page
$text: the text that will be displayed, in HTML (string)

'OutputPageBodyAttributes': called when OutputPage::headElement is creating the body
tag to allow for extensions to add attributes to the body of the page they might
need. Or to allow building extensions to add body classes that aren't of high
enough demand to be included in core.
$out: The OutputPage which called the hook, can be used to get the real title
$sk: The Skin that called OutputPage::headElement
&$bodyAttrs: An array of attributes for the body tag passed to Html::openElement

'OutputPageCheckLastModified': when checking if the page has been modified
since the last visit
&$modifiedTimes: array of timestamps.
	The following keys are set: page, user, epoch

'OutputPageParserOutput': after adding a parserOutput to $wgOut
$out: OutputPage instance (object)
$parserOutput: parserOutput instance being added in $out

'OutputPageMakeCategoryLinks': links are about to be generated for the page's
categories. Implementations should return false if they generate the category
links, so the default link generation is skipped.
$out: OutputPage instance (object)
$categories: associative array, keys are category names, values are category
	types ("normal" or "hidden")
$links: array, intended to hold the result. Must be an associative array with
	category types as keys and arrays of HTML links as values.

'PageContentLanguage': allows changing the language in which the content of
a page is written. Defaults to the wiki content language ($wgContLang).
$title: Title object
&$pageLang: the page content language (either an object or a language code)
$wgLang: the user language

'PageHistoryBeforeList': When a history page list is about to be constructed.
$article: the article that the history is loading for

'PageHistoryLineEnding' : right before the end <li> is added to a history line
$row: the revision row for this line
$s: the string representing this parsed line
$classes: array containing the <li> element classes

'PageHistoryPager::getQueryInfo': when a history pager query parameter set
is constructed
$pager: the pager
$queryInfo: the query parameters

'PageRenderingHash': alter the parser cache option hash key
A parser extension which depends on user options should install
this hook and append its values to the key.
$hash: reference to a hash key string which can be modified

'ParserAfterStrip': Same as ParserBeforeStrip

'ParserAfterTidy': Called after Parser::tidy() in Parser::parse()
$parser: Parser object being used
$text: text that'll be returned

'ParserBeforeInternalParse': called at the beginning of Parser::internalParse()
$parser: Parser object
$text: text to parse
$stripState: StripState instance being used

'ParserBeforeStrip': Called at start of parsing time
(no more strip, deprecated ?)
$parser: parser object
$text: text being parsed
$stripState: stripState used (object)

'ParserBeforeTidy': called before tidy and custom tags replacements
$parser: Parser object being used
$text: actual text

'ParserClearState': called at the end of Parser::clearState()
$parser: Parser object being cleared

'ParserFirstCallInit': called when the parser initialises for the first time
&$parser: Parser object being cleared

'ParserGetVariableValueSwitch': called when the parser need the value of a
custom magic word
$parser: Parser object
$varCache: array to store the value in case of multiples calls of the
	same magic word
$index: index (string) of the magic
$ret: value of the magic word (the hook should set it)
$frame: PPFrame object to use for expanding any template variables

'ParserGetVariableValueTs': use this to change the value of the time for the
{{LOCAL...}} magic word
$parser: Parser object
$time: actual time (timestamp)

'ParserGetVariableValueVarCache': use this to change the value of the
variable cache or return false to not use it
$parser: Parser object
$varCache: varaiable cache (array)

'ParserLimitReport': called at the end of Parser:parse() when the parser will
include comments about size of the text parsed
$parser: Parser object
$limitReport: text that will be included (without comment tags)

'ParserMakeImageParams': Called before the parser make an image link, use this
to modify the parameters of the image.
$title: title object representing the file
$file: file object that will be used to create the image
&$params: 2-D array of parameters

'ParserTestParser': called when creating a new instance of Parser in
maintenance/parserTests.inc
$parser: Parser object created

'ParserTestTables': alter the list of tables to duplicate when parser tests
are run. Use when page save hooks require the presence of custom tables
to ensure that tests continue to run properly.
&$tables: array of table names

'PersonalUrls': Alter the user-specific navigation links (e.g. "my page,
my talk page, my contributions" etc).

&$personal_urls: Array of link specifiers (see SkinTemplate.php)
&$title: Title object representing the current page

'PingLimiter': Allows extensions to override the results of User::pingLimiter()
&$user : User performing the action
$action : Action being performed
&$result : Whether or not the action should be prevented
Change $result and return false to give a definitive answer, otherwise
the built-in rate limiting checks are used, if enabled.

'PrefixSearchBackend': Override the title prefix search used for OpenSearch and
AJAX search suggestions. Put results into &$results outparam and return false.
$ns : array of int namespace keys to search in
$search : search term (not guaranteed to be conveniently normalized)
$limit : maximum number of results to return
&$results : out param: array of page names (strings)

'PrefsEmailAudit': called when user changes his email address
$user: User (object) changing his email address
$oldaddr: old email address (string)
$newaddr: new email address (string)

'PrefsPasswordAudit': called when user changes his password
$user: User (object) changing his passoword
$newPass: new password
$error: error (string) 'badretype', 'wrongpassword', 'error' or 'success'

'ProtectionForm::buildForm': called after all protection type fieldsets are made in the form
$article: the title being (un)protected
$output: a string of the form HTML so far

'ProtectionForm::save': called when a protection form is submitted
$article: the title being (un)protected
$errorMsg: an html message string of an error

'ProtectionForm::showLogExtract': called after the protection log extract is shown
$article: the page the form is shown for
$out: OutputPage object

'ResourceLoaderRegisterModules': Right before modules information is required, such as when responding to a resource
loader request or generating HTML output.
&$resourceLoader: ResourceLoader object

'ResourceLoaderGetStartupModules': Run once the startup module is being generated. This allows you
to add modules to the startup module. This hook should be used sparingly since any module added here
will be loaded on all pages. This hook is useful if you want to make code available to module loader 
scripts. 

'RawPageViewBeforeOutput': Right before the text is blown out in action=raw
&$obj: RawPage object
&$text: The text that's going to be the output

'RecentChange_save': called at the end of RecentChange::save()
$recentChange: RecentChange object

'ResourceLoaderGetConfigVars': called at the end of
ResourceLoaderStartUpModule::getConfig(). Use this to export static
configuration variables to JavaScript. Things that depend on the current
page/request state must be added through MakeGlobalVariablesScript instead.
&$vars: array( variable name => value )

'RevisionInsertComplete': called after a revision is inserted into the DB
&$revision: the Revision
$data: the data stored in old_text.  The meaning depends on $flags: if external
  is set, it's the URL of the revision text in external storage; otherwise,
  it's the revision text itself.  In either case, if gzip is set, the revision
  text is gzipped.
$flags: a comma-delimited list of strings representing the options used.  May
  include: utf8 (this will always be set for new revisions); gzip; external.

'SearchUpdate': Prior to search update completion
$id : Page id
$namespace : Page namespace
$title : Page title
$text : Current text being indexed

'SearchGetNearMatchBefore': Perform exact-title-matches in "go" searches before the normal operations
$allSearchTerms : Array of the search terms in all content languages
&$titleResult : Outparam; the value to return. A Title object or null.

'SearchGetNearMatch': An extra chance for exact-title-matches in "go" searches if nothing was found
$term : Search term string
&$title : Outparam; set to $title object and return false for a match

'SearchGetNearMatchComplete': A chance to modify exact-title-matches in "go" searches
$term : Search term string
&$title : Current Title object that is being returned (null if none found).

'SearchEngineReplacePrefixesComplete': Run after SearchEngine::replacePrefixes().
$searchEngine : The SearchEngine object. Users of this hooks will be interested 
in the $searchEngine->namespaces array.
$query : Original query.
&$parsed : Resultant query with the prefixes stripped.

'SearchableNamespaces': An option to modify which namespaces are searchable.
&$arr : Array of namespaces ($nsId => $name) which will be used.

'SetupAfterCache': Called in Setup.php, after cache objects are set

'ShowMissingArticle': Called when generating the output for a non-existent page
$article: The article object corresponding to the page

'ShowRawCssJs': Customise the output of raw CSS and JavaScript in page views
$text: Text being shown
$title: Title of the custom script/stylesheet page
$output: Current OutputPage object

'ShowSearchHitTitle': Customise display of search hit title/link.
&$title: Title to link to
&$text: Text to use for the link
$result: The search result
$terms: The search terms entered
$page: The SpecialSearch object.

'SiteNoticeBefore': Before the sitenotice/anonnotice is composed
&$siteNotice: HTML returned as the sitenotice
$skin: Skin object
Return true to allow the normal method of notice selection/rendering to work,
or change the value of $siteNotice and return false to alter it.

'SiteNoticeAfter': After the sitenotice/anonnotice is composed
&$siteNotice: HTML sitenotice
$skin: Skin object
Alter the contents of $siteNotice to add to/alter the sitenotice/anonnotice.

'SkinAfterBottomScripts': At the end of Skin::bottomScripts()
$skin: Skin object
&$text: bottomScripts Text
Append to $text to add additional text/scripts after the stock bottom scripts.

'SkinAfterContent': Allows extensions to add text after the page content and
article metadata.
&$data: (string) Text to be printed out directly (without parsing)
$skin: Skin object
This hook should work in all skins. Just set the &$data variable to the text
you're going to add.

'SkinBuildSidebar': At the end of Skin::buildSidebar()
$skin: Skin object
&$bar: Sidebar contents
Modify $bar to add or modify sidebar portlets.

'SkinCopyrightFooter': Allow for site and per-namespace customization of copyright notice.
$title: displayed page title
$type: 'normal' or 'history' for old/diff views
&$msg: overridable message; usually 'copyright' or 'history_copyright'. This message must be in HTML format, not wikitext!
&$link: overridable HTML link to be passed into the message as $1
&$forContent: overridable flag if copyright footer is shown in content language. 

'SkinGetPoweredBy'
&$text: additional 'powered by' icons in HTML.
Note: Modern skin does not use the MediaWiki icon but plain text instead
$skin: Skin object

'SkinSubPageSubtitle': At the beginning of Skin::subPageSubtitle()
&$subpages: Subpage links HTML
$skin: Skin object
$out: OutputPage object
If false is returned $subpages will be used instead of the HTML
subPageSubtitle() generates.
If true is returned, $subpages will be ignored and the rest of
subPageSubtitle() will run.

'SkinTemplateBuildNavUrlsNav_urlsAfterPermalink': after creating the
"permanent link" tab
$sktemplate: SkinTemplate object
$nav_urls: array of tabs

Alter the structured navigation links in SkinTemplates, there are three of these hooks called in different spots.
'SkinTemplateNavigation': Called on content pages after the tabs have been added but before before variants have been added
'SkinTemplateNavigation::SpecialPage': Called on special pages after the special tab is added but before variants have been added
'SkinTemplateNavigation::Universal': Called on both content and special pages after variants have been added
&$sktemplate: SkinTemplate object
&$links: Structured navigation links
This is used to alter the navigation for skins which use buildNavigationUrls such as Vector.

'SkinTemplateOutputPageBeforeExec': Before SkinTemplate::outputPage()
starts page output
&$sktemplate: SkinTemplate object
&$tpl: Template engine object

'SkinTemplatePreventOtherActiveTabs': use this to prevent showing active tabs
$sktemplate: SkinTemplate object
$res: set to true to prevent active tabs

'SkinTemplateSetupPageCss': use this to provide per-page CSS
$out: Css to return

'SkinTemplateTabAction': Override SkinTemplate::tabAction().
You can either create your own array, or alter the parameters for
the normal one.
&$sktemplate: The SkinTemplate instance.
$title: Title instance for the page.
$message: Visible label of tab.
$selected: Whether this is a selected tab.
$checkEdit: Whether or not the action=edit query should be added if appropriate.
&$classes: Array of CSS classes to apply.
&$query: Query string to add to link.
&$text: Link text.
&$result: Complete assoc. array if you want to return true.

'SkinTemplateToolboxEnd': Called by SkinTemplate skins after toolbox links have
been rendered (useful for adding more)
$sk: The QuickTemplate based skin template running the hook.
$dummy: Called when SkinTemplateToolboxEnd is used from a BaseTemplate skin,
  extensions that add support for BaseTemplateToolbox should watch for this dummy
  parameter with "$dummy=false" in their code and return without echoing any html
  to avoid creating duplicate toolbox items.

'SoftwareInfo': Called by Special:Version for returning information about
the software
$software: The array of software in format 'name' => 'version'.
	See SpecialVersion::softwareInformation()

'SpecialContributionsBeforeMainOutput': Before the form on Special:Contributions
$id: User identifier

'SpecialListusersDefaultQuery': called right before the end of
UsersPager::getDefaultQuery()
$pager: The UsersPager instance
$query: The query array to be returned

'SpecialListusersFormatRow': called right before the end of
UsersPager::formatRow()
$item: HTML to be returned. Will be wrapped in <li></li> after the hook finishes
$row: Database row object

'SpecialListusersHeader': called before closing the <fieldset> in
UsersPager::getPageHeader()
$pager: The UsersPager instance
$out: The header HTML

'SpecialListusersHeaderForm': called before adding the submit button in
UsersPager::getPageHeader()
$pager: The UsersPager instance
$out: The header HTML

'SpecialListusersQueryInfo': called right before the end of
UsersPager::getQueryInfo()
$pager: The UsersPager instance
$query: The query array to be returned

'SpecialMovepageAfterMove': called after moving a page
$movePage: MovePageForm object
$oldTitle: old title (object)
$newTitle: new title (object)

'SpecialNewpagesConditions': called when building sql query for Special:NewPages
&$special: NewPagesPager object (subclass of ReverseChronologicalPager)
$opts: FormOptions object containing special page options
&$conds: array of WHERE conditionals for query
&tables: array of tables to be queried
&$fields: array of columns to select
&$join_conds: join conditions for the tables

'SpecialNewPagesFilters': called after building form options at NewPages
$special: the special page object
&$filters: associative array of filter definitions. The keys are the HTML name/URL parameters.
Each key maps to an associative array with a 'msg' (message key) and a 'default' value.

'SpecialPage_initList': called when setting up SpecialPage::$mList, use this
hook to remove a core special page
$list: list (array) of core special pages

'SpecialPasswordResetOnSubmit': when executing a form submission on Special:PasswordReset
$users: array of User objects
$data: array of data submitted by the user
&$error: string, error code (message name) used to describe to error (out paramater).
	The hook needs to return false when setting this, otherwise it will have no effect.

'SpecialRandomGetRandomTitle': called during the execution of Special:Random,
use this to change some selection criteria or substitute a different title
&$randstr: The random number from wfRandom()
&$isRedir: Boolean, whether to select a redirect or non-redirect 
&$namespaces: An array of namespace indexes to get the title from
&$extra: An array of extra SQL statements 
&$title: If the hook returns false, a Title object to use instead of the
result from the normal query

'SpecialRecentChangesFilters': called after building form options at RecentChanges
$special: the special page object
&$filters: associative array of filter definitions. The keys are the HTML name/URL parameters.
Each key maps to an associative array with a 'msg' (message key) and a 'default' value.

'SpecialRecentChangesPanel': called when building form options in
SpecialRecentChanges
&$extraOpts: array of added items, to which can be added
$opts: FormOptions for this request

'SpecialRecentChangesQuery': called when building sql query for
SpecialRecentChanges and SpecialRecentChangesLinked
&$conds: array of WHERE conditionals for query
&$tables: array of tables to be queried
&$join_conds: join conditions for the tables
$opts: FormOptions for this request
&$query_options: array of options for the database request
&$select: Array of columns to select

'SpecialSearchCreateLink': called when making the message to create a page or
go to the existing page
$t: title object searched for
&$params: an array of the default message name and page title (as parameter)

'SpecialSearchGo': called when user clicked the "Go"
&$title: title object generated from the text entered by the user
&$term: the search term entered by the user

'SpecialSearchNogomatch': called when user clicked the "Go" button but the
target doesn't exist
&$title: title object generated from the text entered by the user

'SpecialSearchPowerBox': the equivalent of SpecialSearchProfileForm for
the advanced form, a.k.a. power search box
&$showSections: an array to add values with more options to
$term: the search term (not a title object)
$opts: an array of hidden options (containing 'redirs' and 'profile')

'SpecialSearchProfiles': allows modification of search profiles
&$profiles: profiles, which can be modified.

'SpecialSearchProfileForm': allows modification of search profile forms
$search: special page object
&$form: String: form html
$profile: String: current search profile
$term: String: search term
$opts: Array: key => value of hidden options for inclusion in custom forms

'SpecialSearchSetupEngine': allows passing custom data to search engine
$search: special page object
$profile: String: current search profile
$engine: the search engine

'SpecialSearchResults': called before search result display when there
are matches
$term: string of search term
&$titleMatches: empty or SearchResultSet object
&$textMatches: empty or SearchResultSet object

'SpecialSearchNoResults': called before search result display when there are
no matches
$term: string of search term

'SpecialStatsAddExtra': add extra statistic at the end of Special:Statistics
&$extraStats: Array to save the new stats 
              ( $extraStats['<name of statistic>'] => <value>; )

'SpecialUploadComplete': Called after successfully uploading a file from 
Special:Upload
$form: The SpecialUpload object

'SpecialVersionExtensionTypes': called when generating the extensions credits,
use this to change the tables headers
$extTypes: associative array of extensions types

'SpecialWatchlistFilters': called after building form options at Watchlist
$special: the special page object
&$filters: associative array of filter definitions. The keys are the HTML name/URL parameters.
Each key maps to an associative array with a 'msg' (message key) and a 'default' value.

'SpecialWatchlistQuery': called when building sql query for SpecialWatchlist
&$conds: array of WHERE conditionals for query
&$tables: array of tables to be queried
&$join_conds: join conditions for the tables
&$fields: array of query fields

'TestCanonicalRedirect': called when about to force a redirect to a canonical URL for a title when we have no other parameters on the URL. Gives a chance for extensions that alter page view behavior radically to abort that redirect or handle it manually.
$request: WebRequest
$title: Title of the currently found title obj
$output: OutputPage object

'TitleArrayFromResult': called when creating an TitleArray object from a
database result
&$titleArray: set this to an object to override the default object returned
$res: database result used to create the object

'TitleGetRestrictionTypes': Allows extensions to modify the types of protection
  that can be applied.
$title: The title in question.
&$types: The types of protection available.

'TitleMoveComplete': after moving an article (title)
$old: old title
$nt: new title
$user: user who did the move
$pageid: database ID of the page that's been moved
$redirid: database ID of the created redirect

'UndeleteForm::showHistory': called in UndeleteForm::showHistory, after a
PageArchive object has been created but before any further processing is done.
&$archive: PageArchive object
$title: Title object of the page that we're viewing

'UndeleteForm::showRevision': called in UndeleteForm::showRevision, after a
PageArchive object has been created but before any further processing is done.
&$archive: PageArchive object
$title: Title object of the page that we're viewing

'UndeleteForm::undelete': called un UndeleteForm::undelete, after checking that
the site is not in read-only mode, that the Title object is not null and after
a PageArchive object has been constructed but before performing any further
processing.
&$archive: PageArchive object
$title: Title object of the page that we're about to undelete

'UndeleteShowRevision': called when showing a revision in Special:Undelete
$title: title object related to the revision
$rev: revision (object) that will be viewed

'UnknownAction': An unknown "action" has occured (useful for defining
		 your own actions)
$action: action name
$article: article "acted on"

'UnitTestsList': Called when building a list of files with PHPUnit tests
&$files: list of files

'UnwatchArticle': before a watch is removed from an article
$user: user watching
$article: article object to be removed

'UnwatchArticle': after a watch is removed from an article
$user: user that was watching
$article: article object removed

'UnwatchArticleComplete': after a watch is removed from an article
$user: user that watched
$article: article object that was watched

'UploadForm:initial': before the upload form is generated
$form: UploadForm object
You might set the member-variables $uploadFormTextTop and
$uploadFormTextAfterSummary to inject text (HTML) either before
or after the editform.

'UploadForm:BeforeProcessing': at the beginning of processUpload()
$form: UploadForm object
Lets you poke at member variables like $mUploadDescription before the
file is saved.
Do not use this hook to break upload processing. This will return the user to
a blank form with no error message; use UploadVerification and 
UploadVerifyFile instead

'UploadCreateFromRequest': when UploadBase::createFromRequest has been called
$type: (string) the requested upload type
&$className: the class name of the Upload instance to be created

'UploadComplete': when Upload completes an upload
&$upload: an UploadBase child instance

'UploadFormInitDescriptor': after the descriptor for the upload form as been 
	assembled
$descriptor: (array) the HTMLForm descriptor

'UploadFormSourceDescriptors': after the standard source inputs have been 
added to the descriptor
$descriptor: (array) the HTMLForm descriptor

'UploadVerification': additional chances to reject an uploaded file. Consider 
                      using UploadVerifyFile instead.
string $saveName: destination file name
string $tempName: filesystem path to the temporary file for checks
string &$error: output: message key for message to show if upload canceled 
	by returning false. May also be an array, where the first element
	is the message key and the remaining elements are used as parameters to
	the message.

'UploadVerifyFile': extra file verification, based on mime type, etc. Preferred
                    in most cases over UploadVerification.
object $upload: an instance of UploadBase, with all info about the upload
string $mime: the uploaded file's mime type, as detected by MediaWiki. Handlers 
	will typically only apply for specific mime types.
object &$error: output: true if the file is valid. Otherwise, an indexed array
	representing the problem with the file, where the first element
	is the message key and the remaining elements are used as parameters to
	the message.

'UploadComplete': Upon completion of a file upload
$uploadBase: UploadBase (or subclass) object. File can be accessed by
	$uploadBase->getLocalFile().

'User::mailPasswordInternal': before creation and mailing of a user's new
temporary password
$user: the user who sent the message out
$ip: IP of the user who sent the message out
$u: the account whose new password will be set

'UserAddGroup': called when adding a group; return false to override
stock group addition.
$user: the user object that is to have a group added
&$group: the group to add, can be modified

'UserArrayFromResult': called when creating an UserArray object from a
database result
&$userArray: set this to an object to override the default object returned
$res: database result used to create the object

'userCan': To interrupt/advise the "user can do X to Y article" check.
If you want to display an error message, try getUserPermissionsErrors.
$title: Title object being checked against
$user : Current user object
$action: Action being checked
$result: Pointer to result returned if hook returns false. If null is returned,
	userCan checks are continued by internal code.

'UserCanSendEmail': To override User::canSendEmail() permission check
$user: User (object) whose permission is being checked
&$canSend: bool set on input, can override on output

'UserClearNewTalkNotification': called when clearing the
"You have new messages!" message, return false to not delete it
$user: User (object) that'll clear the message

'UserComparePasswords': called when checking passwords, return false to
override the default password checks
&$hash: String of the password hash (from the database)
&$password: String of the plaintext password the user entered
&$userId: Integer of the user's ID or Boolean false if the user ID was not
	supplied
&$result: If the hook returns false, this Boolean value will be checked to
	determine if the password was valid

'UserCreateForm': change to manipulate the login form
$template: SimpleTemplate instance for the form

'UserCryptPassword': called when hashing a password, return false to implement
your own hashing method
&$password: String of the plaintext password to encrypt
&$salt: String of the password salt or Boolean false if no salt is provided
&$wgPasswordSalt: Boolean of whether the salt is used in the default
	hashing method
&$hash: If the hook returns false, this String will be used as the hash

'UserEffectiveGroups': Called in User::getEffectiveGroups()
$user: User to get groups for
&$groups: Current effective groups

'UserGetAllRights': after calculating a list of all available rights
&$rights: Array of rights, which may be added to.

'UserGetDefaultOptions': after fetching the core default, this hook is ran
right before returning the options to the caller.
&$defaultOptions: Array of preference keys and their default values. 

'UserGetEmail': called when getting an user email address
$user: User object
&$email: email, change this to override local email

'UserGetEmailAuthenticationTimestamp': called when getting the timestamp of
email authentification
$user: User object
&$timestamp: timestamp, change this to override local email authentification
	timestamp

'UserGetImplicitGroups': Called in User::getImplicitGroups()
&$groups: List of implicit (automatically-assigned) groups

'UserGetLanguageObject': Called when getting user's interface language object
$user: User object
&$code: Langauge code that will be used to create the object

'UserGetReservedNames': allows to modify $wgReservedUsernames at run time
&$reservedUsernames: $wgReservedUsernames

'UserGetRights': Called in User::getRights()
$user: User to get rights for
&$rights: Current rights

'UserIsBlockedFrom': Check if a user is blocked from a specific page (for specific block
	exemptions).
$user: User in question
$title: Title of the page in question
&$blocked: Out-param, whether or not the user is blocked from that page.
&$allowUsertalk: If the user is blocked, whether or not the block allows users to edit their
                  own user talk pages.

'UserIsBlockedGlobally': Check if user is blocked on all wikis.
&$user: User object
$ip: User's IP address
&$blocked: Whether the user is blocked, to be modified by the hook

'UserLoadAfterLoadFromSession': called to authenticate users on
external/environmental means; occurs after session is loaded
$user: user object being loaded

'UserLoadDefaults': called when loading a default user
$user: user object
$name: user name

'UserLoadFromDatabase': called when loading a user from the database
$user: user object
&$s: database query object

'UserLoadFromSession': called to authenticate users on external/environmental
means; occurs before session is loaded
$user: user object being loaded
&$result: set this to a boolean value to abort the normal authentification
	process

'UserLoadOptions': when user options/preferences are being loaded from
the database.
$user: User object
&$options: Options, can be modified.

'UserLoginComplete': after a user has logged in
$user: the user object that was created on login
$inject_html: Any HTML to inject after the "logged in" message.

'UserLoginForm': change to manipulate the login form
$template: SimpleTemplate instance for the form

'UserLogout': before a user logs out
$user: the user object that is about to be logged out

'UserLogoutComplete': after a user has logged out
$user: the user object _after_ logout (won't have name, ID, etc.)
$inject_html: Any HTML to inject after the "logged out" message.
$oldName: name of the user before logout (string)

'UserRemoveGroup': called when removing a group; return false to override
stock group removal.
$user: the user object that is to have a group removed
&$group: the group to be removed, can be modified

'UserRights': After a user's group memberships are changed
$user  : User object that was changed
$add   : Array of strings corresponding to groups added
$remove: Array of strings corresponding to groups removed

'UserRetrieveNewTalks': called when retrieving "You have new messages!"
message(s)
$user: user retrieving new talks messages
$talks: array of new talks page(s)

'UserSaveSettings': called when saving user settings
$user: User object

'UserSaveOptions': Called just before saving user preferences/options.
$user: User object
&$options: Options, modifiable

'UserSetCookies': called when setting user cookies
$user: User object
&$session: session array, will be added to $_SESSION
&$cookies: cookies array mapping cookie name to its value

'UserSetEmail': called when changing user email address
$user: User object
&$email: new email, change this to override new email address

'UserSetEmailAuthenticationTimestamp': called when setting the timestamp
of email authentification
$user: User object
&$timestamp: new timestamp, change this to override local email
authentification timestamp

'WantedPages::getQueryInfo': called in WantedPagesPage::getQueryInfo(), can be
used to alter the SQL query which gets the list of wanted pages
&$wantedPages: WantedPagesPage object
&$query: query array, see QueryPage::getQueryInfo() for format documentation

'WatchArticle': before a watch is added to an article
$user: user that will watch
$article: article object to be watched

'WatchArticleComplete': after a watch is added to an article
$user: user that watched
$article: article object watched

'WatchlistEditorBuildRemoveLine': when building remove lines in
	Special:Watchlist/edit
&$tools: array of extra links
$title: Title object
$redirect: whether the page is a redirect
$skin: Skin object

'WikiExporter::dumpStableQuery': Get the SELECT query for "stable" revisions
dumps
One, and only one hook should set this, and return false.
&$tables: Database tables to use in the SELECT query
&$opts: Options to use for the query
&$join: Join conditions

'wgQueryPages': called when initialising $wgQueryPages, use this to add new
query pages to be updated with maintenance/updateSpecialPages.php
$query: $wgQueryPages itself

'XmlDumpWriterOpenPage': Called at the end of XmlDumpWriter::openPage, to allow extra
 metadata to be added.
$obj: The XmlDumpWriter object.
&$out: The output string.
$row: The database row for the page.
$title: The title of the page.

'XmlDumpWriterWriteRevision': Called at the end of a revision in an XML dump, to add extra
 metadata.
$obj: The XmlDumpWriter object.
&$out: The text being output.
$row: The database row for the revision.
$text: The revision text.

'XMPGetInfo': Called when obtaining the list of XMP tags to extract. Can be used to add
	additional tags to extract.
&$items: Array containing information on which items to extract. See XMPInfo for details on the format.

'XMPGetResults': Called just before returning the results array of parsing xmp data. Can be
	used to post-process the results.
&$data: Array of metadata sections (such as $data['xmp-general']) each section is an array of
	metadata tags returned (each tag is either a value, or an array of values).

More hooks might be available but undocumented, you can execute
./maintenance/findhooks.php to find hidden one.