使用用戶名登錄應用程序時，不使用電子郵件，因此會拋出以下錯誤，反之亦然“注意：未定義索引：電子郵件在 /Applications/XAMPP/xamppfiles/htdocs/menthor/login.php 中的第 16 行”我試過將產生錯誤的行放在條件中，但這些努力證明是徒勞的 Login.php 文件（與錯誤相關的部分）// STEP 1. Receive data / info paassed to current fileif ((empty($_REQUEST['username']) || empty($_REQUEST['password'])) && (empty($_REQUEST['email']) || empty($_REQUEST['password']))) {    $return['status'] = '400';    $return['message'] = 'Missing requird information';    echo json_encode($return);    return;} // securing received info / data from hackers or injections$email = htmlentities($_REQUEST['email']);$username = htmlentities($_REQUEST['username']);$password = htmlentities($_REQUEST['password']);// STEP 2. Establish connection with the serverrequire('secure/access.php');$access = new access('localhost' , 'root', '' , 'menthor');$access->connect();// STEP 3. Check existence of the user. Try to fetch the user with the same email address// STEP 3. Check availability of the login/user information$username_aval = $access->selectUser_Username($username);$email_aval = $access->selectUser_Email($email);//$return = array();// user is foundif ($username_aval) {    // Get encrypted password and salt from the server for validation    $encryptedPassword = $username_aval['password'];    $salt = $username_aval['salt'];通過 Web 服務器登錄時的當前結果Notice: Undefined index: email in /Applications/XAMPP/xamppfiles/htdocs/menthor/login.php on line 16{"status":"200","message":"Successfully Logged In","id":"44","username":"rondell","email":"[email protected]","fullName":"rondell","lastName":"","birthday":"","gender":"","cover":"","ava":"","bio":"","allow_follow":"1"}預期成績{"status":"200","message":"Successfully Logged In","id":"44","username":"rondell","email":"[email protected]","fullName":"rondell","lastName":"","birthday":"","gender":"","cover":"","ava":"","bio":"","allow_follow":"1"}