I have a regexp who finds a blocks of bbCode. #\\[(b|u|i|code|color|anothertag|anothertag2|etc)(\s=?.+?|=.+?|)] ( (?: (?R) | (?:.*?(?!\\\[/\\1])) )* ) \\[/\\1]#x for example [ b ]sfsf[ u ]sddgdg[ /u ]dfgdfg[ /b ] It works on pcre 6.2 very well but if i run it on pcre 6.7(php 5.2) and use text like this [ b ]sdfsdf[ i ]dgdfg[ /b ]dfgdg[ /i ...