The difference and connection between session_register_shutdown() and register_shutdown_function()

In PHP development, it is very important to handle operations when a program is closed, especially resource release and data storage. The two functions session_register_shutdown() and register_shutdown_function() are often mentioned, but their functions, usage and applicable scenarios are different. This article will introduce their differences, connections and application in detail.

1. Function introduction

1. register_shutdown_function()

This is a common function provided by PHP, which is used to register a callback function, which is automatically called after the execution of the PHP script. You can register multiple callbacks, and the order of registration determines the order of call.

Sample code:

 <?php
register_shutdown_function(function() {
    echo "The script is executed，Perform a cleanup operation。";
});
?>

When the PHP script is executed, this registered callback function will be executed regardless of whether it ends normally or a fatal error occurs.

2. session_register_shutdown()

This is a function specifically used for the session module. It calls register_shutdown_function() internally and automatically registers the session shutdown handler function to ensure that PHP correctly closes and saves session data at the end of the script.

After PHP 5.4, this function has been marked as discarded and is not recommended to continue using it.

Sample code:

 <?php
session_start();
session_register_shutdown();
$_SESSION['name'] = 'Zhang San';
?>

After being called, the session module will automatically perform a writeback operation at the end of the script.

2. The difference between the two

3. The connection between the two

session_register_shutdown() is actually an encapsulation of register_shutdown_function() , specifically used to ensure that session data can be safely written at the end of the script. Both of these are triggered during the PHP execution flow shutdown phase and belong to the mechanism of script shutdown hook.

Simply put:

• session_register_shutdown() = register_shutdown_function() + session close logic

• Use session_register_shutdown() to allow developers to manually manage session write operations

4. Use scenarios

1. register_shutdown_function()

• Logging, cleaning resources, closing database connections and other operations are required at the end of the script.

• Aftermath operations performed after handling exceptions or fatal errors.

• Customize any function that needs to be executed when the script is closed.

Example:

 <?php
register_shutdown_function(function() {
    error_log("End of script execution，Write to log");
});
?>

2. session_register_shutdown()

• Only suitable for automatic registration session writeback of old versions of PHP (5.3 and before).

• It is not recommended to use the new version. It is recommended to call session_write_close() or rely on PHP to automatically write.

5. Summary

In modern PHP development, it is recommended to use session_write_close() directly when handling session writes. For other cleaning work during closing, register_shutdown_function() is recommended to ensure code compatibility and flexibility.

Additional Note: URL Domain Name Replacement Example

If the code involves URLs, for example:

 <?php
echo "Visit the website: http://example.com/path";
?>

It should be replaced by: