$re = '/^[0-9\)\(\s+-]+(\s?(?:x|extension|ext\.)\s?[0-9-]+)?$/mi';
$str = '555-555-5555
555-555-5555 x55555
555-555-5555x55555
555-555-5555 extension 55555
555-555-5555 ext. 55555
(555) 555-5555
5555555555
555-5555
5555555
1-800-CONTACTS
1-800-555-5555
Hello world
(555-555-5555
0-999-0349300
+43 984-899-46515
+43 some bogus
939403 03904 aosdf
';
preg_match_all($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