JSONP解决JS跨域

<?php
$jsondata = "{symbol:'IBM', price:120}";
echo $_GET['callback'].'('.$jsondata.')';

?>

<script type="text/javascript" src="front/Scripts/jquery-1.4.4.min.js"></script>
<script>
$.getJSON("http://xxxxx.com/testing/jsonp.php?callback=?", function(data) {
    alert(data.price);
});
</script>