How to call a PHP function when “onchange” event is fired?

Question

I have three identical drop down lists that I'm populating using MySQL data. If one of them changes index (onchange is fired), I want the other two to re-populate, so that they exclude the item that has been chosen with the other drop down list.

In ASP.NET, I would simply have called a function (passing through the chosen items' value) in the code behind to re-populate the other two.

I've been poking around for a while now and I just can't get it done with PHP. Does PHP allow function calling from this event? I've also tried using AJAX, but nothing.

Answer 1

OnChange() is a js function , in order to use it to call a php function you'll have to use AJAX . Using ajax you'll be able to get the php's code returned value , display it in the page , or doing whatever manipulation you'd like.

Good luck

Answer 2

You can't (directly) call server side functions from the client side.

You can make an HTTP request to a URL that runs a server side script that calls the function.

ASP.NET has (I believe, I've never used it) some stuff that will set up a URL and generate some JavaScript that will call that URL for you.

There is nothing in the PHP core to do that.

A very rough, quick and dirty outline (that makes no attempt to be RESTful) of how you might go about doing something like that would be:

 callFunction.php:
 <?php
     include("myFunctions.php");
     if ($_GET['call'] == "functionA") {
         functionA();
     }
 ?>

Then your JS would make an ajax request to callFunction.php?call=functionA .

Answer 3

ASP.NET would have been doing a Postback when the dropdown was changed, although you'd not have had to write it explicitly.

If you want to do a round trip to the server in PHP, you'll have to implememnt the same logic (eg post the form with JavaScript in the onchange event).

This is a good situation for using AJAX as well, but you haven't provided any details of what you tried or what went wrong so it's hard to help further.