$.ajax({

    dataType: "jsonp",

    url: "http://www.b.com/b.php",

    jsonp: "callback",

    success: function(data) {

        $(".info").text("uid:" + data.uid + " name:" + data.name);

    }

});

$callback = !empty($_GET['callback']) ? trim($_GET['callback']) : '';

if(!empty($callback)) {

    $data = json_encode(array(

        'uid' => 1,

        'name' => '测试',

    ));

    echo $callback."({$data});";

}