$re = '/(?<days>\d+(?= д.))?(?<hours>\d+(?= ч.))?(?<minutes>\d+(?= м.))?/u';
$str = '5 д. 1 ч. 23 м.
17 ч. 44 м.
12 д. 17 ч.';
preg_match_all($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