$re = '/(([0-9]{1,2}|[a-z]{1,3})-([0-9]{2,3}|[a-z]{2,3})-([0-9]{1,2}|[a-z]{1,2}))/i';
$str = 'XX-99-99
2 1965 99-99-XX
3 1973 99-XX-99
4 1978 XX-99-XX
5 1991 XX-XX-99
6 1999 99-XX-XX
7 2005 99-XXX-9
8 2009 9-XXX-99
9 2006 XX-999-X
10 2008 X-999-XX
11 2015 XXX-99-X';
preg_match_all($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