PHP: format Phone Number

phone.php

function format_phone($phone)
{
	$phone = preg_replace("/[^0-9]/", "", $phone);

	if(strlen($phone) == 7)
		return preg_replace("/([0-9]{3})([0-9]{4})/", "$1-$2", $phone);
	elseif(strlen($phone) == 10)
		return preg_replace("/([0-9]{3})([0-9]{3})([0-9]{4})/", "($1) $2-$3", $phone);
	else
		return $phone;
}