$re = '/^(?:(?:[01]?[0-9]|2[0-3]):[0-5][0-9](?:[ECMP]ST|UTC)|\d+(?:\.\d+)?[mh])$/m';
$str = '0:30EST
00:30PST
22:15MST
13:51UTC
12.5m
555h
---
33:47EST
1:25GMT
123:56EST
12:356EST
AB
EST
h
55.55.55h';
preg_match_all($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