$re = '/((?P<Days>\d{0,2})d\s*)?((?P<Hours>\d{0,2})h\s*)?((?P<Mins>\d{0,2})m)?/m';
$str = '1d 12m
43m
1d 10h 20m
20h 10m
5h
2d';
preg_match_all($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