$re = '/((?:[A-Z]{2}-\d{2}-\d{2})|(?:\d{2}-[A-Z]{2}-\d{2})|(?:\d{2}-\d{2}-[A-Z]{2}))/';
$str = '00-00-AA
AA-00-00
00-AA-00';
preg_match_all($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