Description:
------------
---
From manual page: http://www.php.net/reference.pcre.pattern.modifiers
---

"""
u (PCRE_UTF8)
This modifier turns on additional functionality of PCRE that is incompatible with Perl. Pattern strings are treated as UTF-8. This modifier is available from PHP 4.1.0 or greater on Unix and from PHP 4.2.3 on win32. UTF-8 validity of the pattern is checked since PHP 4.3.5.
"""

Since the utf8 modifier is available since 4.1.0 (!!) one would expect utf8 support to work since that version unless otherwise stated in the documentation. (otherwise, what does one want a modifier for utf8 for, if utf8 is not supported?)

No mention is done in this page that utf8 regular expressions on utf8 strings won't work in PHP versions prior to 5.3, but that is the case.

See http://3v4l.org/ERDp5

Either utf8 is only supported as of 5.3.4, or there was a bug that rendered it useless that has only been fixed in 5.3.4.

In either case, this must be documented with a gigantic red warning in this page.