Creating jQuery AJAX requests to a PHP function

Question

So far when creating AJAX requests I have been posting to a separate PHP file. Is it possible to create a jQuery AJAX request that calls a PHP function rather than posts to a separate page?

If you could send me any examples or documentation would be great.

Answer 1

I believe there's a fundamental misunderstanding of how the technology works here.

AJAX (Javascript), Flash, or any client-sided technology cannot directly call PHP functions (or other languages running on the server). This is true for going the other way around as well (eg: PHP can't call JS functions).

Client and server codes reside on different machines, and they communicate through the HTTP protocol (or what have you). HTTP works roughly like this:

Client (eg: browser) sends a REQUEST -> Server processes request and sends a RESPONSE -> Client gets and displays and/or processes the response

You have to see these requests and responses as messages. Messages cannot call functions on a server-side language directly ¹, but can furnish enough information for them to do so and get a meaningful message back from the server.

So you could have a handler that processes and dispatches these requests, like so:

// ajax_handler.php
switch ($_POST['action']) {
    case 'post_comment':
        post_comment($_POST['content']);
        break;
    case '....':
        some_function();
        break;
    default:
        output_error('invalid request');
        break;
}

Then just have your client post requests to this centralized handler with the correct parameters. Then the handler decides what functions to call on the server side, and finally it sends a response back to the client.

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¹ Technically there are remote procedure calls (RPCs), but these can get messy.

Answer 2

AJAX requests call a URL (make a HTTP request), not a file, in most cases the URL is translated by the server to point at a file (or a php script in your case), but everything that happens from the HTTP request to the response that is received is up to you (on your server).

There are many PHP frameworks that map URL's to specific php functions, AJAX is just an asynchronous way to access a URL and receive a response.

Said URL CAN trigger the server to call a specific function and send back a response. But it is up to you to structure your URL's and server side code as such.