我写了这个简单的Restful web服务，却得到了一个空白的回复.为什么?

我正在学习用PHP编写Restful Web服务。因此，我遵循了一个视频教程，并编写了以下基本的Web服务。问题是，当我尝试通过http://localhost/Test8/?name=c（因为我的index.php位于Test8目录中）URL访问web服务时，我会得到一个空白页面。

但当视频中的导师使用http://localhost/rest/?name=c访问时（因为他们的index.php位于rest目录中），他们在网页中获得了{"status":200, "status_message":"Book found", "data":348}

我错过了什么

index.php:

<?php
//Process client's request (via URL)
header("Content-Type:application/json");
if (  !empty($GET['name'])  ) {
    $name = $GET['name'];
    $price = get_price($name);
    if (empty($price)) {
        //Book not found
        deliver_response(200, 'Book not found!', NULL);
    } else {
        //Send the response with book price
        deliver_response(200, 'Book found', $price);
    }
} else {
    //throw invalid request
    deliver_response(400, "Invalid Request", NULL);
}

 //API Functions
 function get_price($bookRequested) {
     $books = array(
        'Java' => 999,
        'C' => 348,
        'PHP' =>500
     );
     foreach ($books as $book=>$price) {
         if ($book == $bookRequested) {
             return $price;
         }
     }
 }

 function deliver_response($status, $status_message, $data) {
     header("HTTP/1.1 $status $status_message");
     $response['status'] = $status;
     $response['status_message'] = $status_message;
     $response['data'] = $data;
     $json_response = json_encode($response);
 }
?>

编辑：

刚刚检查了控制台。上面写着Failed to load resource: the server responded with a status of 400 (Invalid Request)

我更改了

if (  !empty($GET['name'])  ) {
    ...
} else {
    //throw invalid request
    ...
}

到

if (  !empty($GET['name'])  ) {
    echo '$GET["name"] is NOT empty';
    ...
} else {
    echo '$GET["name"] IS empty';
    //throw invalid request
    ...
}

并且浏览器打印$GET["name"] IS empty