Question

I have a javascript file and I want to call a function on the php server side and return the result back to the client side using ajax, but I am not sure how to make the request to the specific php function.

Here are my files:

The javascript file basically retrieves the username from the html form, and I want to send that username to php and check against the database for availability.

In something.js:

function check_availability()
{
    var username = $.trim(document.getElementById('usernameField').value);
    var xmlhttp= new XMLHttpRequest();

    // not sure how to make the request here to check_availability() under php
}

The PHP file will just check the username thats being passed from the js file against the database, if its available return true, else false.

In something.php:

    class Something_Model {
    private $data;
    private $table;

    public function __construct() {
        $this->data = new udata(DBSERVER, DBUSERNAME, DBPASSWORD, DBNAME);
    }

    # check for username availability
    public function check_availability()
    {
        // make the check here, but needs to retrieve username from js file
        echo "here";
    }
}

So, inside the Something_Model class, I want to make the check_availability() call from javascript, can someone give me an example to make this ajax call? Also, how do I return the result back to the javascript? Do I need to encode it as a JSON obj?

Thanks a lot.

Answer 1

You can’t call a function in PHP directly – but you can call a PHP page that in turn can call the PHP function. For example…

service.php

include_once('something.php');
$model = new Something_Model();
$model->check_availability();

something.js

function check_availability() {

    var request = new XMLHttpRequest();
    request.open('GET', 'http://yoursite/service.php', false);
    request.send();

    if (request.status === 200) {
      alert(request.responseText);
    }
}

I have used a really simple example of an XMLHttpRequest – this example actually blocks while the request is made. In reality you may want to use a callback and allow it to run asynchronously but I wanted to keep the answer as short as possible.