$re = '/(\S+), (\S+)(.*(?!,)).*?\n/';
$str = 'lastname1, firstname1 middlename1
lastname1, firstname1 middlename1 lastname2, firstname2 middlename2
lastname1, firstname1
lastname1, firstname1 lastname2, firstname2
lastname1, firstname1 lastname2, firstname2
';
preg_match_all($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