Let's talk about the problem of deleting wrong user names and passwords on php web pages-PHP Problem-php.cn

Let's talk about the problem of deleting wrong user names and passwords on php web pages

PHPz

Release： 2023-03-31 10:02:49

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With the development of the Internet, more and more people are beginning to use PHP to develop web pages. However, when we write a PHP web page, we may encounter a very common problem: unable to delete username and password errors.

This is because when we design the login page, we usually store the username and password in the backend database, and then when the user logs in, we send an HTTP request to the backend server to verify whether the username and password are correct. If the username and password are incorrect, the server will return a corresponding error message, but we cannot return the error message to the front-end interface for display.

So, how to solve this problem?

First, we need to add some code to the background PHP script to capture error information. The specific method is as follows:

//connect to database
$server = "localhost";
$username = "root";
$password = "your_password";
$dbname = "your_database";
$mysqli = new mysqli($server, $username, $password, $dbname);

//check connection
if ($mysqli->connect_error) {
    die("Connection failed: " . $mysqli->connect_error);
}

//process login request
$username = $_POST["username"];
$password = $_POST["password"];
$sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = $mysqli->query($sql);

if ($result->num_rows > 0) {
    //login success
    echo "Welcome, " . $username . "!";
} else {
    //login failed
    echo "Username or password is incorrect.";
}

Copy after login

In the above code, we connect to the MySQL database by using the mysqli class in PHP, and match the entered username and password with the username and password in the database. If the username and password match successfully, a welcome message is returned, otherwise an error message is returned.

However, when we visit the login page, the error message still cannot be displayed in the front-end page. Therefore, we need to use AJAX technology to pass error information from the back-end PHP script to the front-end interface.

The specific method is as follows:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Login Form</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script>
        function login() {
            var username = $("#username").val();
            var password = $("#password").val();
            $.post("process_login.php", {username: username, password: password}, function(data) {
                $("#result").html(data);
            });
        }
    </script>
</head>
<body>
    <h1>Login Form</h1>
    <form>
        <label>Username:</label><input type="text" id="username"><br>
        <label>Password:</label><input type="password" id="password"><br>
        <button type="button" onclick="login()">Login</button>
    </form>
    <div id="result"></div>
</body>
</html>

Copy after login

In the above code, we use jQuery AJAX technology to send the entered user name and password to the background PHP script through HTTP POST request, and will return The results are displayed on the front-end page.

Therefore, when the username and password are entered incorrectly, the error message will be transmitted to the front-end page, thereby solving the problem that we cannot delete the username and password errors.

In short, the above is how to solve the problem of how to delete wrong username and password in PHP web pages. This is a very beneficial exercise for beginners who want to improve their PHP programming skills.

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