PHP Identify JSON Post

Hi,

i´m struggling atm with the simple action of sending the json data from the enfmp tagger to the server.

"&#95" => _

$file =file_get_contents('./test.json');
$jsondecode = json_decode($file,true );
foreach($jsondecode as $puffer) {
  $result = $puffer['code'];
}
$post = array(
     "api_key"=>"=MYAPIKEY",
     "version"=>"=3.15",
     "code"=>"=$result",
);
$ch = curl_init();
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_URL, "http://developer.echonest.com/api/v4/song/identify");
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post); 
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded'));

$json_response = curl_exec($ch);
$response = json_decode($json_response, true);

The Response is

  ["response"]=>
  array(1) {
    ["status"]=>
    array(3) {
      ["version"]=>
      string(3) "4.2"
      ["code"]=>
      int(1)
      ["message"]=>
      string(22) "1|Invalid key: Unknown"
    }
  }
}

Can someone look over the code and give me some hints or examples?

greetings :)