Passing Javascript Variable (var ...) to PHP Variable ($...) using Ajax - php

Question

I'm having a problem in passing variable from Javascript to PHP,
passing variables from PHP to Javascript is Easy
but is there a way to pass Variables from Javascript to PHP?
Here's the Situation
Think of this as the variables of the first select input
--2010
--2011
--2012
and
the Values of the second select group varies depending on the selected option
of the first select group
The values are:
2010
--AAA
--AAB
--AAC
2011
--ABA
--ABB
--ABC
2012
--ACA
--ACB
--ACC
say that the values are displayed by a conditional PHP function that
retrieves data from a Database
Here's What I Want to do:
When I Select One from the first select Group,
It will change the options of the second select group
of course, this happens via triggers when the first select group changes
I need to Retrieve the value of the first select group to filter the data
that will be displayed as the options of the second Group which comes from
a database and a PHP function is made to process it, thats why i need the value
of the first select group and use it as a parameter for the second select group.
The Problem:
i need to get the value of the first select group in PHP Varible
to make a PHP Function work.
Please Help!!!

Answer 1

You can simply add it in as a url parameter in the ajax request that you send.
Consider your first field is like so:
<select id="field1">
<option value="2010">2010</option>
<option value="2011">2011</option>
<option value="2012">2012</option>
</select>
Your javascript will be like so:
var ajaxUrl="http://myserver.com/getfield2.php?field1=" + document.getElementById("field1").value;
And then you will send the ajax request to ajaxUrl
In the php, you will get this value as
$_GET["field1"]

Answer 2

Like said above, your fields are
<select id="field1">
<option value="2010">2010</option>
<option value="2011">2011</option>
<option value="2012">2012</option>
</select>
Use jQuery to perform an AJAX call to your script. Something like that
$("#field1").change(function(){
var value = $(this).val();
$.post('script.php', {
phpvar: value
}, function(){
//this is callback, render your second field here, with the responce of php script
});
});
In your php script, variable passed from jQuery will be available like this
$_POST['phpvar']