$re = '/^(\[WIP\])?(\[PIDSS-\d+]) [[:upper:]].{3,}/m';
$str = '[PIDSS-12345] Blah blah
[PIDSS-1] Blah blah
[PIDSS-] Blah blah
^(?![A-Z]).+$
[WIP][PIDSS-1] Blah blah
[WIP]';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php