<?php
echo 'hi';
$_GET['id'];
?>
<script src="jquery.js"></script>
<script>

$(function (){

	var id=10;
	$.ajax({

	url: 'something.php',

	data: { 'id' : id}, //send id

	success: function(data) {
	$('#stu_name').val(data.name);
	},
	dataType: 'json' //also can be xml

	});


})
</script>

<form action='jquery.php' method='GET'>
	ID: <input type='text' name='id'>
	Name:<input type='text' name='stu_name'>
</form>