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In PHP, using Memcached as session preservation is a common practice, which can improve session processing efficiency and stability in distributed environments. To ensure that session data can be correctly written to the cache after script execution, the session_register_shutdown() function plays a key role. This article will introduce in detail how to use this function correctly and what to note during use.
session_register_shutdown() is a built-in function in PHP. Its purpose is to register a closed callback function, which is used to automatically call session_write_close() to ensure that session data is properly saved and closed at the end of script execution.
Usually, PHP will automatically call session_write_close() at the end of the script, but in some cases, such as exit midway, or when there is complex logic processing, automatic closing may fail or cause data to not be saved in time. By explicitly calling session_register_shutdown() , the session can be guaranteed to be safely written at the end of the script.
When using Memcached to save session, PHP's session handler will serialize the session data and save it into Memcached. The configuration is usually as follows:
ini_set('session.save_handler', 'memcached');
ini_set('session.save_path', 'm66.net:11211');
session_start();
At this time, the read and write operations of the session are completed through Memcached, and session_write_close() is responsible for writing the session data in memory back to Memcached.
The correct call time is to call it immediately after session_start() , so that PHP will register a closed callback function, and automatically call session_write_close() at the end of the script. Sample code:
<?php
// Setting up use Memcached As session keep
ini_set('session.save_handler', 'memcached');
ini_set('session.save_path', 'm66.net:11211');
session_start();
session_register_shutdown(); // Automatically write when registration is closed session
// operate session
$_SESSION['user'] = 'Zhang San';
// At the end of the script，session 数据会自动keep到 Memcached
Note that it must be called after session_start() , otherwise the function will not work.
Make sure Memcached service is available
The Memcached server must be running normally and reachable, otherwise the session read and write will fail, affecting the user experience.
Avoid repeated registration after manually calling session_write_close() <br> If session_write_close() is manually called in the script, calling session_register_shutdown() will not make sense and may lead to unexpected behavior.
PHP Version Compatibility
session_register_shutdown() is built in PHP 5.4.0 and above, and older versions require custom closing callbacks.
Error handling
Memcached storage failure will not throw exceptions. It is recommended to monitor the Memcached status through logs to prevent session data loss.
Avoid unreasonable session expiration time setting <br> The expiration time of the Memcached server needs to be configured according to business needs, otherwise the session may expire prematurely.
When using Memcached as the session, it is recommended to call session_register_shutdown() after session_start() to ensure that session is automatically written back to Memcached at the end of the script.
Ensure the stability of Memcached service and set the session expiration time reasonably.
Be careful to avoid repeated calls to session_write_close() and ensure PHP version supports it.
Through log monitoring, cache exceptions can be discovered in a timely manner to ensure the security of session data.
This will give full play to the advantages of Memcached's high-performance distributed cache and achieve stable and efficient session management.
