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How to solve the problem when PHP prompts that the account and password are incorrect but does not disappear?

PHPzOriginal: 2023-03-22 15:22:481230browse

PHP is a popular programming language used for developing web applications. When developing web applications, user authentication is often required. Due to the importance of account security, when a user submits an incorrect username or password, corresponding prompt information should be given in a timely manner. However, sometimes we encounter a problem, that is, even if the user enters the correct username and password, the error message still does not disappear. There are many possible reasons for this situation. This article will analyze this problem and give corresponding solutions.

1. Cause analysis

First, let us see why the error message still does not disappear after the user enters the correct user name and password. There are two main possible reasons for this situation:

1.1. The page does not reload

When the user enters the wrong username or password, the PHP code will usually store the error message in the session variable or cookie and redirect the page back to the login page. The purpose of this is to allow the user to see the error message and enter the correct username and password again. If the user enters the correct username and password, the page will be redirected to another page, so the original error message stored in the session variable or cookie cannot be read again. This is one of the reasons why the error message won't go away.

1.2. Implementation problem

Another possible reason is that there is a problem with the way the error message is displayed in the PHP code. If the error message is hard-coded in the code without using corresponding variables to store it, then during the login process, the same error message will be displayed regardless of whether the user enters the correct username and password.

2. Solution

We already know the two reasons why the error message does not disappear. Next, we will introduce two solutions to solve this problem.

2.1. Load a new page

In order to ensure that the error information in the session variables or cookies is cleared after the user enters the correct username and password, we need to add a line of code to the PHP code, Used to check if there is an error message and redirect to another page if there is no error message.

Sample code:

<?php
session_start(); // 开启会话
if (isset($_SESSION[&#39;error_message&#39;]) && !empty($_SESSION[&#39;error_message&#39;])) {
    $error_message = $_SESSION[&#39;error_message&#39;];
    unset($_SESSION[&#39;error_message&#39;]); // 清除错误信息
} else {
    $error_message = &#39;&#39;; // 没有错误信息
}
if (isset($_POST[&#39;username&#39;]) && isset($_POST[&#39;password&#39;])) {
    // 验证用户输入
} else {
    header(&#39;Location: login.php&#39;); // 重定向到登录页面
}
?>
<!DOCTYPE html>
<html>
<head>
    <title>Login</title>
</head>
<body>
    <form method="post">
        <label for="username">Username:</label>
        <input type="text" name="username" id="username" />
        <label for="password">Password:</label>
        <input type="password" name="password" id="password" />
        <input type="submit" value="Login" />
    </form>
    <?php if (!empty($error_message)): ?>
        <div class="error"><?php echo $error_message; ?></div>
    <?php endif; ?>
</body>
</html>

In the above sample code, we check whether $_SESSION['error_message'] exists. If it exists, we store it in another variable $error_message and display it on the page. Then, we use the unset() function to clear the session variable that stores the error information. If no error message exists, $error_message will be an empty string.

2.2. Use variables to store error information

Another solution is to use variables to store error information in PHP code. In this case, we don't need to check if an error message exists, we have to reset the corresponding variables on every login request.

Sample code:

<?php
if (isset($_POST[&#39;username&#39;]) && isset($_POST[&#39;password&#39;])) {
    // 验证用户输入
    $error_message = &#39;&#39;; // 初始化错误提示信息
    if ($input_is_error) {
        $error_message = &#39;Invalid username or password&#39;;
    } else {
        // 登录成功
    }
} else {
    header(&#39;Location: login.php&#39;); // 重定向到登录页面
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>Login</title>
</head>
<body>
    <form method="post">
        <label for="username">Username:</label>
        <input type="text" name="username" id="username" />
        <label for="password">Password:</label>
        <input type="password" name="password" id="password" />
        <input type="submit" value="Login" />
    </form>
    <?php if (!empty($error_message)): ?>
        <div class="error"><?php echo $error_message; ?></div>
    <?php endif; ?>
</body>
</html>

In the above sample code, we use the $error_message variable in the PHP code to store the error message, and it must be reset on every login request. If the user does not enter the correct username and password, $error_message will be set to the corresponding error message. If the login is successful, $error_message will be reset to an empty string.

3. Conclusion

In PHP development, there is a problem that the error message does not disappear. The main reason is that the page is not reloaded or there is a problem with the implementation method. In order to solve this problem, we can check the error message variable or use a variable to store the error message. Either way, you can effectively solve this problem and ensure that the error message is cleared after the user enters the correct username and password.

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