$re = '/((?:Mo|Tu|We|Th|Fr|Sa|Su)+)\s*[\d: PM-]{17}/';
$str = 'MoWe 04:30PM - 05:50PM
Fr 12:00PM - 01:20PM';
preg_match_all($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