json_decode出现问题

Question

For some reason I cannot seem to get json_decode to pull out the id I need. Perhaps I have a syntax error in this code? The code otherwise works. If I manually provide the id in between the two API calls it completes successfully. Also, I have not really been able to easily debug this because I am calling this PHP function using ajax and an html button and I dont really know Ajax at all, so I dont know how to print debug echo messages in the PHP code as I usually would to see where I am having trouble. So basically I am troubleshooting this blind.

Basically the code does an initial API call to find the VM with the tag "VMTAG". The API call returns JSON info for that VM. I extract the ID with json_decode, then I do a second API call shutting down the VM using that ID.

function shutdown() {
    $ch = curl_init('https://api.digitalocean.com/v2/droplets?tag_name=VMTAG');
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET");
    curl_setopt($ch, CURLOPT_HTTPHEADER, array(
        'Authorization: Bearer TOKENHIDDEN',
        'Content-Type: application/json')
    );
    $json = curl_exec($ch);
    $object = json_decode($json);
    $id = $object['id'];
    $data = array("type" => "shutdown");
    $data_string = json_encode($data);
    $ch = curl_init('https://api.digitalocean.com/v2/droplets/' . $id . '/actions');
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array(
        'Authorization: Bearer TOKENHIDDEN',
        'Content-Type: application/json',
        'Content-Length: ' . strlen($data_string))
    );
    $result = curl_exec($ch);
    exit;
} 

Answer 1

You have

$object = json_decode($json); // this gives a stdClass
$id = $object['id'];          // you are using $object as an assoc. array

instead,

$object = json_decode($json,true); // now you have an assoc array and 
$id = $object['id'];               // $id should now be defined

see the docs for json_decode :

http://php.net/manual/en/function.json-decode.php