$re = '/(G1:k6YxekrAP71LqRv)\[(?:S:(?:\d,)+\d\|)?(P:3)(?:\|R:(?:\d,)+\d)?\]/m';
$str = 'G1:k6YxekrAP71LqRv[P:3]
G1:k6YxekrAP71LqRv[S:2,3,4|P:3]
G1:k6YxekrAP71LqRv[P:3|R:2,3,4,5]
G1:k6YxekrAP71LqRv[S:2,3,4|P:3|R:2,3,4,5]';
preg_match_all($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