preg replace - Are the PHP preg_functions multibyte safe?

Question

There are no multibyte 'preg' functions available in PHP, so does that mean the default preg_functions are all mb safe? Couldn't find any mention in the php documentation.

Answer 1

pcre supports utf8 out of the box, see documentation for the 'u' modifier.

Illustration (xC3xA4 is the utf8 encoding for the german letter "?")

  echo preg_replace('~w~', '@', "axC3xA4b");

this echoes "@@¤@" because "xC3" and "xA4" were treated as distinct symbols

  echo preg_replace('~w~u', '@', "axC3xA4b");

(note the 'u') prints "@@@" because "xC3xA4" were treated as a single letter.