How Does PDO Close Database Connections?

PDO Connection Closure

Unlike MySQLi, PDO does not provide an explicit close() function to terminate the database connection. Instead, it implements a more streamlined approach for closing connections.

PDO's Null Assignment:

In PDO, closing a connection involves setting the connection variable to null. This simple assignment notifies the PHP Garbage Collector to mark the connection object for removal.

PHP Garbage Collector:

PHP's Garbage Collector manages memory deallocation automatically. Once the connection variable is set to null, the Garbage Collector identifies the connection object as unusable and removes it from memory. This process frees up the resources associated with the connection.

Automatic Connection Closure:

It is important to note that PDO can automatically close connections when your script ends. This behavior is triggered by the PHP interpreter's end-of-script termination sequence. If you do not explicitly set the connection variable to null, PDO will automatically close it upon script completion.

Persistent Connections:

However, if you initialize your PDO object as a persistent connection, the automatic connection closing behavior will not occur. In this case, you will need to manually set the connection variable to null to release the connection resources.

Conclusion:

PDO's null assignment approach for closing connections offers a simple and efficient way to manage database connections. By setting the connection variable to null, you initiate the process of freeing up the associated resources, while PHP's Garbage Collector handles the actual deallocation. This approach ensures that your database connections are closed properly without the need for explicit close() function calls.

The above is the detailed content of How Does PDO Close Database Connections?. For more information, please follow other related articles on the PHP Chinese website!