What are some potential security risks associated with allowing users to log in only once with the same credentials in PHP?

Allowing users to log in only once with the same credentials in PHP can lead to potential security risks such as session hijacking and unauthorized access if an attacker gains access to a user's credentials. To mitigate this risk, you can implement session regeneration after a successful login to invalidate the old session and create a new one. 

session_start();

// Check if user credentials are valid
if ($valid_credentials) {
    // Regenerate session ID to prevent session fixation
    session_regenerate_id(true);
    
    // Store user information in session
    $_SESSION['user_id'] = $user_id;
    
    // Redirect to dashboard or homepage
    header('Location: dashboard.php');
    exit();
} else {
    // Invalid credentials, show error message
    echo 'Invalid username or password';
}

Keywords

PHP security risks user authentication session management credential reuse

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