$re = '/(?:(?:[0-9A-Fa-f]{2}(?=([-:\.]|))(?:\1[0-9A-Fa-f]{2}){5}))/m';
$str = '13:14:5f:cD:42:5f
13-14-5f-cD-42-5f
13.14.5f.cD.42.5f
13145fcD425f
13-145f:cD425f';
preg_match_all($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