怎么使用post提交json数据

$post_data =   

            array(  

                    'name'=>'aaa',  

                    'age'=>45,  

            );  

  



    $url='http://www.example.com/example.php';  

  

    $ch = curl_init();  

    curl_setopt($ch, CURLOPT_POST, 1);  

    curl_setopt($ch, CURLOPT_URL,$url);  

    curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);  

    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

    $result=curl_exec($ch);  

    echo $result;