Information processing instructions for php custom Session

When using Session technology to track users in the system, the default processing method of Session is to record the session information of each user in the file in the Web server, and create the path of the session data file through session.save_path in php.ini. Although this default processing method is convenient, it is also flawed. It will seriously affect the execution efficiency of the system. The main reason is that the own Session mechanism cannot be used across machines, because for systems with relatively large access volume, multiple servers are usually used for concurrent processing. If each server processes the Session separately, the purpose of tracking users cannot be achieved. At this time, you need to change the way Session is processed. You can save Session information to other servers using sharing technology, or use a database to save Session information.

Whether you use a database or sharing technology to share Session information, the principle is basically the same, and the default processing method is changed through thesession_set_save_handler()function in PHP , specify a callback function to customize processing. The function is as follows:

session_set_save_handler(open, close, read, write, destroy, gc)

This function requires a total of 6 callback functions as required parameters, which represent the 6 processes in the Session life cycle. By customizing each function, you can set

Information processing in each link of the Session life cycle.

##Callback function Description open Executed when running session_start(). This tax needs to declare two parameters. The system will automatically pass the session.save_path option value in php.ini to the first parameter of the function, and the session name will be automatically passed to the second parameter. Return true to continue execution. close This function does not require parameters and is executed when the script execution is completed or session_write_close() or session_destroy() is called, that is, after all Session operations are completed. implement. If no processing is required, return true directly. read Executed when running session_start(), because when the session is opened, the current session data will be read and written to the $_SESSION variable. A parameter needs to be declared, and the system will automatically pass the Session ID to this function, which is used to obtain the corresponding user data through the Session ID, and return the session information of the current user and write it into the $_SESSION variable write This function is executed when the script ends and the $_SESSION variable is assigned a value. Two parameters need to be declared, namely Session ID and serialized session information string. When assigning a value to the $_SESSION variable, you can find the storage location through the Session ID and write the information. Return true after successful storage and continue to execute destroy When running session_destroy(), you need to declare a parameter, and the system will automatically pass the Session ID to This function is used to delete the corresponding session information. gc Executed when the garbage collection program starts. A parameter needs to be declared, and the system will pass the session.gc_maxlifetime option value in php.ini to this function to delete Session information that exceeds this time. Return true to continue execution. Explanation: When running

session_start(), open (start the session) and read (read the current session data and write to $_SESSION) are executed respectively ) and gc (garbage cleaning) operations, all operations on $_SESSION in the script will not call these callback functions. When calling thesession_destroy()function, execute destroy to destroy the current session (usually deleting the response records or files), but this callback function only destroys the session data. At this time, if# is output ##$_SESSION variable still has a value, but this value will not be written back after close. Execute write and close when calling the

session_wrte_close()

function, and save $_SESSION to storage. If not used manually, it will be automatically executed at the end of the script.

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