Thread:Project:Support desk/Cannot edit pages/reply (4)

OK, in fact it looks like it is exactly this error: https://bugzilla.wikimedia.org/show_bug.cgi?id=58213 The fix will be part of MediaWiki 1.22.2.

The interesting info is that PHP 5.4 by default includes PCRE 8.32 and that according to the bug report, the problem should only arise with older versions of PCRE, but not with 8.32. Since you have the problem anyway, I guess that your PHP version is compiled with an older version of PCRE, see Manual:Errors_and_symptoms/PCRE.

Note that staying with the old version of PCRE is no solution for you: With the fix for bug 58213, MediaWiki will require at least PCRE version 7.2; it will no longer work with older versions.