php sets session save time

In website development, session is a very important mechanism. It can help the website save the user's login information, shopping cart data and other similar information to maintain data consistency while the user browses the website. Normally, the session storage time is very short-lived because once the user closes the browser, the session will be destroyed. But in some cases where user information needs to be saved for a long time, we need to set the session storage time. This article will introduce how to set the session storage time of PHP.

1. session storage time

Session depends on cookies, so we can indirectly control the session storage time by setting the cookie expiration time. When a page saves a session in a cookie, the cookie is stored on the user's machine for a specific period of time and is cleared by the browser after expiration. In this way, the session will be destroyed because the corresponding cookie cannot be found.

By default, the expiration time of a cookie is during the browser session, which means that the cookie will always exist as long as the browser is not closed. But by setting the expiration time of the cookie, we can control the storage time of the cookie and thus the storage time of the session. Here is an example:

// 设置过期时间为30天
$expire_time = time() + 60 * 60 * 24 * 30;
setcookie('session_id', session_id(), $expire_time);

In this case, we use the setcookie function to set the session_id cookie so that the session can still be accessed after the browser is closed. The $expire_time variable is set to the current timestamp in seconds plus the number of seconds in 30 days, i.e. this cookie will expire in 30 days.

2. session.gc_maxlifetime

We can also set the maximum lifetime of the session by modifying the session.gc_maxlifetime option in the php.ini file. This option specifies the maximum session lifetime, in seconds. When a session expires, that is, after this time has passed, it will be automatically destroyed by PHP's garbage collection mechanism. By default, the value of this option is 1440 seconds (that is, 24 minutes). We can modify this value in the php.ini file as follows:

session.gc_maxlifetime = 1800

This will make all sessions have 30 Minutes of storage time, if longer time is required, this value can be set to a larger value.

It should be noted that if we set the maximum session lifetime time too long, it may occupy too many server resources and cause the server load to be too high.

3. session_set_cookie_params

In addition to using the setcookie function to set the expiration time of the cookie and setting the maximum lifetime of the session by modifying the session.gc_maxlifetime option in the php.ini file, we You can also use the session_set_cookie_params function provided by PHP to set some parameters of the cookie, thereby indirectly controlling the session storage time. This function accepts 4 parameters:

session_set_cookie_params($lifetime, $path, $domain, $secure);

Among them:

• $lifetime: cookie lifetime, in seconds;
• $path: cookie path;
• $domain: The domain name of the cookie;
• $secure: Whether the cookie can only be sent through the HTTPS protocol.

When we use the session_start function to start the session, these parameters will take effect to control the storage time of the session. The following is a sample code that uses the session_set_cookie_params function to set the cookie lifetime:

// 设置cookie的路径为整个域名，生存时间为1小时
session_set_cookie_params(3600, '/');
session_start();

In this example, we set the cookie lifetime to 1 hour and the cookie path to the entire domain name. After such settings, the session will Saved on the client during this time period. This approach is more flexible than directly setting the cookie expiration time, because we can also modify the cookie path and domain name at any time to finely control the session storage time.

4. Summary

Session is a very important mechanism in Web development. It can provide many useful features for the website, such as user authentication, shopping cart, etc. If we need to save user information for a long period of time, we need to control the session storage time. In PHP, we can achieve this by setting the cookie expiration time, modifying the session.gc_maxlifetime option in the php.ini file, or using the session_set_cookie_params function. It should be noted that too long session storage time may increase the load of the server and cause server problems, so we should set the session storage time reasonably according to actual needs.

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