Google API-PHP的URL缩短器

我的代码如下。 URL缩短服务有效，但是当我插入 $ POST 时无效。有人知道如何解决此问题吗？

My code is below. The URL shortening service works, but it doesn't when I insert my $POST. Does anyone know how to fix this my looking at the code?

// This is the URL you want to shorten
$longUrl = 'http://www.mysite.com/XXXXX/XX/$_POST['qrname']';

// Get API key from : http://code.google.com/apis/console/
$apiKey = 'MyAPIKey';

$postData = array('longUrl' => $longUrl, 'key' => $apiKey);
$jsonData = json_encode($postData);

$curlObj = curl_init();

curl_setopt($curlObj, CURLOPT_URL, 'https://www.googleapis.com/urlshortener/v1/url');
curl_setopt($curlObj, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curlObj, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($curlObj, CURLOPT_HEADER, 0);
curl_setopt($curlObj, CURLOPT_HTTPHEADER, array('Content-type:application/json'));
curl_setopt($curlObj, CURLOPT_POST, 1);
curl_setopt($curlObj, CURLOPT_POSTFIELDS, $jsonData);

$response = curl_exec($curlObj);

// Change the response json string to object
$json = json_decode($response);

curl_close($curlObj);

echo 'Shortened URL is: '.$json->id;