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Use header() + session_start() to do login jump

M66 2025-06-02

In web development, page redirection after user login is a very common feature. Using PHP, we can manage the user's login status through session_start() , and then combine the header() function to realize page redirection. This article will explain how to implement this function step by step.

1. Understand session and header

  • session_start()
    session_start() is a method used in PHP to start a session. It will save user information on the server side, such as user name, user ID, etc., so as to identify the same user in multiple requests.

  • header()
    header() is a function used by PHP to send raw HTTP header information. One of the common uses is to send a Location header, which allows the browser to jump to another page.

Need to note:

  • header() must be called before outputting anything, including spaces or HTML.

  • session_start() should also be called before any output.

2. Implementation steps

Suppose we have a simple login form, and after logging in successfully, we need to jump to the user's personal homepage.

Login form page (login.php)

 <?php
// Open session
session_start();
?>
<!DOCTYPE html>
<html>
<head>
    <title>User login</title>
</head>
<body>
<form method="post" action="login_process.php">
    username: <input type="text" name="username"><br>
    password: <input type="password" name="password"><br>
    <input type="submit" value="Log in">
</form>
</body>
</html>

Login processing page (login_process.php)

 <?php
session_start();

// 模拟的username和password
$correct_username = 'admin';
$correct_password = '123456';

// Get the submitted data
$username = $_POST['username'] ?? '';
$password = $_POST['password'] ?? '';

// 检查username和password是否正确
if ($username === $correct_username && $password === $correct_password) {
    // Log in成功，set up session
    $_SESSION['username'] = $username;

    // Jump to user homepage
    header('Location: https://m66.net/user_home.php');
    exit;
} else {
    // Log in失败，跳转回Log in页
    header('Location: https://m66.net/login.php?error=1');
    exit;
}
?>

User homepage (user_home.php)

 <?php
session_start();

// 检查是否已Log in
if (!isset($_SESSION['username'])) {
    // 如果没有Log in，跳转到Log in页面
    header('Location: https://m66.net/login.php');
    exit;
}

$username = $_SESSION['username'];
?>
<!DOCTYPE html>
<html>
<head>
    <title>welcome，<?php echo htmlspecialchars($username); ?></title>
</head>
<body>
<h1>welcome回来，<?php echo htmlspecialchars($username); ?>！</h1>
<p><a href="logout.php">退出Log in</a></p>
</body>
</html>

Logout page (logout.php)

 <?php
session_start();
session_unset();
session_destroy();

// 跳转回Log in页面
header('Location: https://m66.net/login.php');
exit;
?>

3. Things to note

  • Call header() and session_start() before output
    As long as there is any output on the page (including HTML, spaces, line breaks, etc.), header() and session_start() will report an error. Make sure they are called at the top of the file.

  • Security <br> In the example code, the user name and password are written dead. In actual projects, they should be retrieved from the database and used encryption (such as password_hash() and password_verify() ).

  • Log out <br> Be sure to clean the session when exiting, otherwise the user status will still exist even if you jump back to the login page.

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