更新：有人在评论中提出建议后，它现在可以工作了。我仍然无法使用index.php文件中的登录/注销按钮。当我登录时，请确认密码，但不显示注销按钮。它显示了index.php中的错误（我已经注释掉了该行）it says undefined index name非常感谢任何帮助。
我的网站上有注册和登录表格。我能够正确注册，并且将密码存储为哈希值。当我尝试登录时，总是说错密码。我假设我输入的密码正确无误，因此我的代码可能有问题。
index.php
<?php
session_start();
error_reporting(E_ALL);
ini_set('display_errors', '1');
require "navigationbar.php";
require "loginpage.php";
?>
<html>
<head>
<link href="https://fonts.googleapis.com/css2?family=Dancing+Script&display=swap" rel="stylesheet">
<link
rel="stylesheet"
href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css"
/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"></script>
<script src="https://use.fontawesome.com/releases/v5.0.8/js/all.js"></script>
<link href="stylee.css" rel="stylesheet" />
<link href="https://fonts.googleapis.com/css2?family=Raleway:wght@100&display=swap" rel="stylesheet">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
</head>
<body>
<?php
$user = $_SESSION['name'] ; //it says undefined index name
if (isset($user )) {
echo '<p>You are logged in</p>';
echo '<form action="logout.php" method="post">
<button type="submit" name="logout-submit">Logout</button>
</form>';
<link href="stylee.css" rel="stylesheet" />
<form action="logoutbackend.php" method="post">
<button type="submit" name="logout-submit" class="logout_button">Logout</button>
</form>';
} else {
echo '<p class="login-status">You are logged out!</p>';
echo '<div class="login-container">
<form action="./backend/loginbackend.php" method="post">
<div class="form-group row">
<div class="col-sm-10">
<h2>website</h2>
</div>
</div>
<div class="form-group row">
<div class="col-sm-10">
<input type="email" class="form-control" name="email" placeholder="Email">
</div>
</div>
<div class="form-group row">
<div class="col-sm-10" >
<input type="password" class="form-control" name="password" placeholder="password">
</div>
</div>
<div class="form-group row">
<div class="col-sm-10">
<button type="submit" class="btn btn-primary" name="login_submit">Log In</button>
</div>
</div>
</form>
<div class="form-group row">
<div class="col-sm-10">
<p>New to <span>ShowCo</span>?<a class="open-button" onclick="openForm()">Sign up</a> </p>
</div>
</div>
<div class="form-popup" id="myForm">
<form action="./backend/signupbackend.php" class="form-container" method="post">
<div class="form-group row">
<div class="col-sm-10" >
<h1>Sign up</h1>
</div>
</div>
<div class="form-group row">
<div class="col-sm-10" >
<input type="text" class="form-control" placeholder="Username" name="username" required>
</div>
</div>
<div class="form-group row">
<div class="col-sm-10" >
<input type="email"class="form-control" placeholder="Email address" name="mail" required>
</div>
</div>
<div class="form-group row">
<div class="col-sm-10" >
<input type="password" class="form-control" placeholder="Password" name="password" required>
</div>
</div>
<div class="form-group row">
<div class="col-sm-10" >
<input type="password" class="form-control" placeholder="Repeat password" name="repeatpassword" required>
</div>
</div>
<div class="form-group row">
<div class="col-sm-10" >
<button type="submit" class="btn btn-primary" name="signup_submit">Sign up</button>
</div>
</div>
<button type="button" class="close" aria-label="Close" onclick="closeForm()"><span aria-hidden="true">×</span></button>
</form>
</div>
</div>
<script>
function openForm() {
document.getElementById("myForm").style.display = "block";
}
function closeForm() {
document.getElementById("myForm").style.display = "none";
}
</script>
';
}
?>
</body>
</html>
<?php
require "footer.php";
?>
Signupbackend.php
<?php
if(isset($_POST["signup_submit"])) {
require "../database_files/database_for_signup.php";
require "../index.php";
$username = $_POST['username'];
$email = $_POST['mail'];
$password = $_POST['password'];
$repeatPassword = $_POST['repeatpassword'];
if (empty($username) || empty($email) || empty($password) || empty($repeatPassword)) {
header("Location: ../index.php?error=emptyfields&username=" .$username."&mail=" .$email);
exit();
} else if(!filter_var($email, FILTER_VALIDATE_EMAIL) && !preg_match("/^[a-zA-Z0-9]*$/",$username)) {
header("Location: ../index.php?error=invalidmailusername");
exit();
} else if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
header("Location: ../index.php?error=invalidmail&username=".$username);
exit();
} else if (!preg_match("/^[a-zA-Z0-9]*$/",$username)) {
header("Location: ../index.php?error=invalidusername&mail=".$email);
exit();
} else if($password != $repeatPassword) {
header("Location: ../index.php?error=passwordcheck&username=".$username."&mail=".$email);
exit();
} else {
$sql = "SELECT COUNT(username) AS num FROM signup_info WHERE username = :username";
$stmt = $conn->prepare($sql);
$stmt->bindValue(':username', $username);
$stmt->execute();
$row = $stmt->fetch(PDO::FETCH_ASSOC);
if ($row['num'] > 0) {
die('Sorry, username already exists. Please try a different username');
}
$passwordHash = password_hash($pass, PASSWORD_BCRYPT, array("cost" => 12));
$sql = "INSERT INTO signup_info(username, email, password) VALUES (:username, :email, :password)";
$stmt = $conn->prepare($sql);
$stmt->bindValue(':username', $username);
$stmt->bindValue(':email', $email);
$stmt->bindValue(':password', $passwordHash);
$result = $stmt->execute();
if($result) {
echo "Registered!";
}
}
}
?>
Loginbackend.php
<?php
if(isset($_POST['login_submit'])) {
require "../database_files/database_for_signup.php";
$email = $_POST['email'];
$password = $_POST['password'];
if ((empty($username)) || (empty($password))) {
echo 'empty username/password';
die();
}
$sql = 'SELECT username, email, password FROM signup_info WHERE email = :email';
if ($stmt = $conn->prepare($sql)) {
$stmt->bindParam(':email', $email, PDO::PARAM_STR);
if ($stmt->execute()) {
if($stmt->rowCount() == 1) {
if ($row = $stmt->fetch()) {
$hashed_password = $row['password'];
if(password_verify($password, $hashed_password)) {
session_start();
$_SESSION['email'] = $email;
$_SESSION['name'] = $row['username'];
echo "verfiied";
} else {
echo "wrong password"; }
}
}
}
}
}
?>
logout.php
<?php
session_start();
session_unset();
session_destroy();
header("Location: ./index.php");
请帮助我为什么我无法验证密码？另外，我在SO上也遇到过类似的问题，但没有任何帮助。任何帮助表示赞赏。