getting variable from javascript to php - php

Question

I have a simple combo box whose value I can get in JavaScript.
I am doing that so I don't need to refresh the page.
Also I want to use the selected value to do some conditional branching after combo box so how do I get the value of combo box from JavaScript to my variable $change.
echo '<select id="combo_1">';
echo '<option value="2">Submative</option>';
echo '<option value="1">formative</option>';
echo '</select>';
Below is my JavaScript:
<script type="text/javascript">
$(document).ready(function() {
$('#combo_1').change(function(){
});
});
</script>
Here I want to do $change = $(this).val(), but obviously I cant do it like this.
Any suggestions?
i want to do it on the same page without refreshing or without submitting
my url kinda look like this
http://localhost/lms/grade/report/userdef/index.php
and i want it to be on click action
cuz depending on the choice of combobox 2 very different procedures will be called

Answer 1

You're gonna want to use AJAX and submit the form, then you can access the returned data without ever refreshing the page.
Basically:
HTML
<select name="combo" id="combo_1">
<option value="2">Submative</option>
<option value="1">formative</option>
</select>
JavaScript
$('#combo_1').change(function() {
$.post('calcScript.php', $(this).serialize(), function(data) {
alert(data);
});
});
in PHP, you can access your combo data via $_POST['combo'].

Answer 2

<script type="text/javascript">
$(document).ready(function() {
$('#combo_1').change(function(){
var combo_1 = $(this).val();
$.ajax({
type: 'GET',
url: 'ajax.php',
data: {'combo_1':combo_1},
success: function(data){
alert(data)
}
});
});
});
</script>
ajax.php
if( isset($_GET['combo_1]) ) {
echo $change = $_GET['combo_1'];
}

Answer 3

JS:
$.ajax({
type: "POST",
url: './filename.php',
beforeSend: function(){
//If you want to do something
},
data: 'data='$('#combo_1').val(), //Optional '&data2='+value+'&datan='+value,
success: function(msg){
alert(msg);
}
});
PHP:
$val = $_POST['data'];
return 'received successfully';
This will alert 'received successfully'