How Does a PHP Server Handle Simultaneous Requests?

Simultaneous Requests to PHP Script

When multiple browser requests are made to the same PHP script concurrently, the server's behavior depends on its configuration, but typically it can handle hundreds of such requests simultaneously.

Apache's MaxClients configuration allows the server to limit the number of concurrent requests. Exceeding this limit will usually result in queuing, up to a threshold defined by the ListenBacklog directive. Once a child process completes a request, another queued request will be serviced.

Therefore:

Will the requests be queued?

No, unless:

• A lock is present, such as when file-based sessions in PHP are used and the session file is locked during a request.
• Requests originate from the same client using the same browser, which may queue requests internally.
• The server reaches the MaxClients limit.

Will they be ignored?

No, allowing multiple users to access the website simultaneously.

Will each request have its own script instance?

There is no such concept as a "script instance." Each process created to handle a request has its own memory space and executes the PHP script independently.

In summary, multiple requests can be handled concurrently without significant conflicts. The server manages the load by queuing requests or limiting the number of concurrent processes.

The above is the detailed content of How Does a PHP Server Handle Simultaneous Requests?. For more information, please follow other related articles on the PHP Chinese website!