$re = '/^((\d)(?!\2)(\d)(?!\2|\3)(\d)(?!\2|\3|\4)(\d)(?!\2|\3|\4|\5)(\d)(?!\2|\3|\4|\5|\6)(\d)(?!\2|\3|\4|\5|\6|\7)(\d)(?!\2|\3|\4|\5|\6|\7|\8)(\d)(?!\2|\3|\4|\5|\6|\7|\8|\9)(\d))(?:,(?1))*
$/mx';
$str = '123456789,123456789,123456789
123456789
123456789,123456789
123456789,123456781
^';
preg_match_all($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