preg match count matches

preg_match already returns the number of times the pattern matched.

However, this will only be 0 or 1 as it stops after the first match. You can use preg_match_all instead as it will check the entire string and return the total number of matches.

You should use preg_match_all if you want to match all occurences. preg_match_all returns number of matches. preg_match returns only 0 or 1, because it matches only once.

$message='[tag] [tag]';
echo preg_match_all('/\\[tag\\](?>\\s|$)/i', $message, $matches);

gives 2. Note you cannot use \b because the word boundary is before the ], not after.

See preg_match_all.