$re = '/((\d{3}|\(\d{3}\))?)(\s|-|\.?)\d{3}(\s|-|\.)\d{4}(\s*(ext|x|ext.)\s*(\d{2,5})?)/';
$str = '123-231-3333 ext 12345';
preg_match_all($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