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In PHP, managing the lifecycle of sessions is a common task, especially when maintaining user state or sharing data across multiple pages. PHP provides two methods to destroy a session: SessionHandler::destroy() and session_destroy(). Although their names are similar, there are important differences in how they work. This article will explain these differences in detail and help you choose the best way to destroy a session.
session_destroy() is a built-in PHP function used to destroy the current session. This function clears all data associated with the current session and deletes the $_SESSION array. Note that session_destroy() only marks the session as destroyed; it does not immediately delete all session data. The data is actually cleared on the next page load.
session_destroy() removes the session data files on the server or deletes records from the database.
It does not delete the data in the $_SESSION array. In fact, the $_SESSION array still exists after the session is destroyed, but it no longer contains valid data.
You must call session_start() to initialize the session; otherwise, session_destroy() cannot be called properly.
<?php
session_start(); // Start the session
<p>// Set session variables<br>
$_SESSION['user'] = 'John Doe';</p>
<p>// Destroy the session<br>
session_destroy();<br>
?>SessionHandler::destroy() is a method used within a custom session handler. When you need control over how sessions are stored (e.g., in a database instead of PHP’s default file storage), you may implement a custom SessionHandler class. In this case, SessionHandler::destroy() destroys session data and triggers the appropriate cleanup operations.
SessionHandler is part of the session_set_save_handler() function, which allows developers to customize session storage. By implementing the destroy() method in a SessionHandler interface, developers define exactly how session destruction occurs.
SessionHandler::destroy() calls the custom destruction operations to ensure session data is removed from the custom storage system.
A custom session handler must be set using session_set_save_handler().
It destroys all data associated with a session ID, usually stored in a database or another storage medium.
<?php
class MySessionHandler extends SessionHandler {
public function destroy($session_id) {
// Custom logic to remove session data, e.g., delete from database
$db = new mysqli("localhost", "user", "password", "database");
$db->query("DELETE FROM sessions WHERE session_id = '$session_id'");
return parent::destroy($session_id);
}
}
// Set custom session handler
session_set_save_handler(new MySessionHandler(), true);
session_start(); // Start the session
// Set session data
$_SESSION['user'] = 'Jane Doe';
// Destroy the session
session_destroy();
?>
Use Cases:
session_destroy() is a built-in PHP function suitable for standard session destruction, especially when no custom session storage is used.
SessionHandler::destroy() is designed for scenarios with custom session storage, allowing developers to implement custom logic for destroying sessions.
Scope of Operation:
session_destroy() only destroys session data but does not remove the $_SESSION array. This means session data still exists for the current request until the page is refreshed.
SessionHandler::destroy() fully destroys session data, usually removing it from the custom storage immediately.
Flexibility:
session_destroy() is simpler and suitable for most common cases.
SessionHandler::destroy() offers higher flexibility and scalability, ideal for complex applications requiring custom storage and destruction operations.
If you are using PHP’s default session storage (such as file storage) and only need to destroy the current session, session_destroy() is the simplest and most straightforward method.
If you are using custom session storage (such as a database) and want complete control over how the session is destroyed, SessionHandler::destroy() is more appropriate.
Overall, session_destroy() is suitable for most typical applications, while SessionHandler::destroy() is better for highly customized scenarios. Which method you choose depends on how you store session data and manage its lifecycle.
