$re = '/^\(?\d{3}\)?\-?\d{3}\-?\d{4}$/m';
$str = '999-999-9999
(123)123-1454
1234567890
(123)1231234
a122-123-1234
(123)-123-12345
(123)-(123)-(1234)';
preg_match_all($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