$re = '/(\w{2}-\d{2}-\d{2})|(\d{2}-\d{2}-\w{2})|(\d{2}-\w{2}-\d{2})|(\w{2}-\d{2}-\w{2})|(\w{2}-\w{2}-\d{2})|(\d{2}-\w{2}-\w{2})|(\d{2}-\w{3}-\d{1})|(\d{1}-\w{3}-\d{2})|(\w{2}-\d{3}-\w{1})|(\w{1}-\d{3}-\w{2})|(\w{3}-\d{2}-\w{1})|(\d{1}-\w{2}-\d{3})/m';
$str = 'XX-99-99
99-99-XX
99-XX-99
XX-99-XX
XX-XX-99
99-XX-XX
99-XXX-9
9-XXX-99
XX-999-X
X-999-XX
XXX-99-X
9-XX-999';
preg_match_all($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