$re = '/^((?:[01][0-9]?)|(?:2[0-4]?)|(?:[3-9]))(?::((?:[0-5][0-9]?)|(?:60))|:)?$/m';
$str = '0
1
12
12:
12:3
12:30
1:
1:3
1:30
2
3
4
5
6
7
8
9
1:60
24:60
24:00
00:60
25:30
00:61';
preg_match_all($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