variable value from javascript to php

I need to get value from Javascript to Php, the scenario is below:

I have a drop-down list which is loaded through ajax call, i couldnot find any means to get the value of selected index value of list to a php variable.

help plz

thanks

 

it's probably not the conventional way but I just use an image tag and load the source, assuming you only need to set a variable and not give a response.

<script type="text/javascript">
    function selchange() {
    document.getElementById("img1").src = "Default.aspx?LID=" + document.getElementById("select1").selectedIndex;
    }
</script>
<img style="display:none" id="img1" />
<select id="Select1" name="D1" onchange="selchange()">
        <option>Option 1</option>
        <option>Option 2</option>
        <option>Option 3</option>
</select>

Code (markup):

I don't use php but you would then have setvar.php which would save the value from the querystring("LID") into a session variable.

 

I have used the hidden input text field as a way to assign the value. It does assign it. BUT, this all (Dropdown list and hidden text field is in iframe and I do not post it) is inside the iframe. I want to get the hiddentext field value on the parent page,

e.g.
<?php
$value = $_POST['hiddentextfield'];
?>