$re = '/^([0-9]+:[0-9]+(?: P)?(?: K)?(?: \+ [0-9]+:[0-9]+(?: P)?(?: K)?)*)$/m';
$str = '15:15
1:0
1:2 K
1:3 P
1:4 P K
3:4 + 3:2
34:14 P K + 3:1 P
15:15 K P + ';
preg_match_all($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