$re = '/\(?\d{3}\)? {0,2}[-.]? {0,2}\d{3} {0,2}[-.]? {0,2}\d{4}/';
$str = '555-555-5555
(555)555-5555
(555) 555-5555
555 -555-5555
(555)555- 5555
(555) 555 -5555
555.555-5555
555.555.5555
5555555555
555-555.5555
(555)5555555
(555).555.5555
(555)-555-5555
(555555-5555
555)-555-5555
555555-5555
555 5555555
555 555 5555
555 - 555 - 5555
555555 . 5555
';
preg_match_all($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