$re = '/# Adding password requirements are as easy as tacking on
# another (?=...) group.
^
(?=(?:[^a-z]*[a-z]){1}) # At least {1} lowercase \'a-z\' letter
(?=(?:[^A-Z]*[A-Z]){2}) # At least {2} uppercase \'A-Z\' letters
(?=(?:[^0-9]*[0-9]){3}) # At least {3} digits
(?=(?:[^\s]*[\s]){1}) # At least {1} whitespace
(?=(?:[^[:punct:]]*[[:punct:]]){1}) # At least {1} special char
(?=.{9}) # A minimum of 9 characters
/mx';
$str = 'See \'unit tests\' to see all matching/non-matching examples.
';
preg_match_all($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