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In web development, user login and logout are one of the most basic and important functions. This article will use a simple example to explain in detail how to use PHP functions to implement a complete user login and logout process.
First, a database needs to be created to save the user's username and password. Here is an example SQL code for creating databases and data tables:
CREATE DATABASE user_info; USE user_info; CREATE TABLE users ( id INT AUTO_INCREMENT PRIMARY KEY, username VARCHAR(255) NOT NULL, password VARCHAR(255) NOT NULL );
Next, a login form page is needed to collect the account number and password entered by the user.
<!DOCTYPE html>
<html>
<head>
<title>Login</title>
</head>
<body>
<h1>Login</h1>
<form action="login.php" method="POST">
<label for="username">Username:</label>
<input type="text" name="username" id="username" required><br>
<label for="password">Password:</label>
<input type="password" name="password" id="password" required><br>
<input type="submit" value="Login">
</form>
</body>
</html>
After the user submits the form, it will jump to the login processing page. This page will verify the account password and enable Session.
<?php
session_start();
// Get form data
$username = $_POST['username'];
$password = $_POST['password'];
// Connect to the database
$mysqli = new mysqli('localhost', 'username', 'password', 'user_info');
// Query user information
$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = $mysqli-> query($query);
//Judge login status if ($result->num_rows == 1) {
$_SESSION['username'] = $username;
header('Location: welcome.php');
} else {
echo 'Invalid username or password.';
}
?>
After logging in successfully, jump to the welcome page. If you are not logged in, you will automatically redirect back to the login page.
<?php
session_start();
if (isset($_SESSION['username'])) {
$username = $_SESSION['username'];
echo "Welcome, $username! ";
echo '<a href="logout.php"> Logout ';
} else {
header('Location: login.php');
}
?>
After the user clicks to log out, the Session should be cleared and redirected back to the login page.
<?php
session_start();
session_unset();
session_destroy();
header('Location: login.php');
?>
Through PHP combined with MySQL database, a simple user login and logout function can be quickly implemented. It is recommended to encrypt and store passwords in actual projects (such as using password_hash() ), add verification code functions, and use prepared statements to prevent SQL injection to enhance system security.
