$re = '/(1?[\(\s\.-]\d{3}\)?[\s\.-]\d{3}[\s\.-]\d{4}(\z[^\d])?)/';
$str = '(408) 394-7557
';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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