/**
 * 隐藏手机号中间4位
 * @param $mobile
 * @return string|string[]|null
 */
final protected function hideMobilePhoneNumber($mobile)
{
    $IsWhat = preg_match('/(0[0-9]{2,3}[\-]?[2-9][0-9]{6,7}[\-]?[0-9]?)/i', $mobile);
    if ($IsWhat == 1) {
        return preg_replace('/(0[0-9]{2,3}[\-]?[2-9])[0-9]{3,4}([0-9]{3}[\-]?[0-9]?)/i', '$1****$2', $mobile);
    } else {
        $pattern = '/(\d{3})(\d{4})(\d{4})/i';
        $replacement = '$1****$3';
        return preg_replace($pattern, $replacement, $mobile);
    }
}