PHP 正则匹配IP

/**
 * 匹配IP地址
 * @param string $subject
 * @return bool
 */
function checkVailIp(string $subject){
    $pattern  = "/(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|[1-9])\.";
    $pattern .="(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|\d)\.";
    $pattern .="(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|\d)\.";
    $pattern .="(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|\d)/";
    if (preg_match($pattern,$subject)){
        return true;
    }else{
        return false;
    }
}