php session principle

php session principle

Session mechanism

session mechanism The solution is to maintain the state on the server side, and has its own corresponding unique identifier session_id to distinguish the previous information of different users.

How Session works

When a session is enabled for the first time, a unique identifier is stored in a local cookie;

First use the session_start() function, PHP loads the stored session variables from the session warehouse;

When the PHP script is executed, register it by using the session_register() function session variable.

When the PHP script execution ends, the session variables that have not been destroyed will be automatically saved in the local session library under a certain path. This path can be passed session.save_path# in the php.ini file. ##Specify that it can be loaded and used next time you browse the web.

Session’s advantages and disadvantages

Advantages

Uniqueness, convenient calling, and not occupying too many resources. It is a group of temporary files stored on the server. data. Under normal circumstances, when we log in as a user, we will store the user data in the session. In this way, it can be easily called on any page, and each client will generate a unique session_id without confusion. And after closing the browser, the server will have a session recycling mechanism to automatically delete expired sessions.

Disadvantages

The client is saved in the form of cookies. If cookies are disabled, the session will become invalid.

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