$re = '/(?P<first1>\w+)[ ](?P<last1>\w+)|(?P<last2>\w+),[ ](?P<first2>\w+)/m';
$str = '"first_name last_name" or "last_name, first_name"';
preg_match_all($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