$re = '/(1\s?)?(\(\d{3}\)\s?|\d{3}[\-|\s]?)(\d{3}[\-|\s]?)(\d{4})/';
$str = '555-555-5555
(555)555-5555
(555) 555-5555
555 555 5555
5555555555
1 555 555 5555
(555-555-5555
1(555)555-5555';
preg_match_all($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