Will using session_set_cookie_params affect an existing PHP session?

1. session_set_cookie_params Function

session_set_cookie_params is used to set various parameters for session cookies. Its basic usage is as follows:

session_set_cookie_params([  
    'lifetime' => 3600, // cookie expiration time (in seconds)  
    'path' => '/', // cookie path  
    'domain' => 'm66.net', // cookie domain  
    'secure' => true, // whether the cookie should be transmitted only via HTTPS  
    'httponly' => true, // prevents client-side JavaScript from accessing the cookie  
]);  

This function affects the generation of the PHP session cookie, and these settings are typically made before calling session_start(). However, does session_set_cookie_params affect an already existing PHP session?

2. Timing of Session Parameter Effect

The session cookie parameters set by session_set_cookie_params only apply to subsequently created sessions. When you call session_start() to start a session, PHP creates a new session cookie. This cookie is generated based on the parameters defined in session_set_cookie_params.

However, if you have already started a session (via session_start()), calling session_set_cookie_params will not affect the cookie used by the current session. The existing session cookie has already been created, and these parameters will only be updated during the next request. Therefore, session_set_cookie_params does not immediately take effect for existing sessions.

3. Example of Effects

Let's assume you call session_set_cookie_params in the following two scenarios:

// First scenario: Setting cookie parameters before starting the session  
session_set_cookie_params([  
    'lifetime' => 3600,  
    'domain' => 'm66.net'  
]);  
session_start();  

In this case, the session cookie will be generated based on the domain and lifetime you set.

But if you have already started a session:

// Second scenario: Calling session_set_cookie_params after starting the session  
session_start(); // Starting the session  
session_set_cookie_params([  
    'domain' => 'm66.net',  
    'lifetime' => 7200  
]);  

In this case, session_set_cookie_params will not affect the current session. The new cookie parameters will only take effect the next time session_start() is called.

4. How to Modify Parameters for an Existing Session?

If you need to modify the parameters of an already existing session (such as changing the cookie's expiration time), you can indirectly control the session content by modifying the values in the $_SESSION array, but you cannot directly change the existing session cookie.

session_start(); // Start the session  
$_SESSION['user'] = 'example'; // Set session content  
// If you need to change the session's expiration time, you can adjust it in the server-side logic,  
// but you cannot directly alter the existing session cookie.