php 端: demo.php
<?php
    $result =array('content'=>$_GET['content']);
    function jsonp($result){
        return $_GET['callback'] . '(' . urldecode(json_encode($result)) . ')';
    }
    echo jsonp($result);
?>


客户端：demo.js
<script>
       $.ajax({
                           url      : 'http://127.0.0.1/demo.php',
                           data     :{'content':'this is a test'},
                           dataType : 'jsonp',
                           jsonp    : 'callback',
                           success  : function(res) {
                                      console.log(res);       
                           }
       });
</script>