"An assertion subpattern is matched in the normal way, except that it does not cause the current matching position to be changed. Lookahead assertions start with (?= for positive assertions and (?! for negative assertions. For example, \w+(?=;) matches a word followed by a semicolon, but does not include the semicolon in the match..."
If you want to match more than once within a single string, you will need to use preg_match_all() and add a subpattern to the regular expression. Let us know if this is the case. Regards, Coop