How to use php curl to obtain a json object and convert it into an array

function objtoarr($obj){
$ret = array();
foreach($obj as $key =>$value){
if(gettype($value) == 'array' || gettype($value) == 'object'){
$ret[$key] = objtoarr($value);
}else{
$ret[$key] = $value;
}
}
return $ret;
}
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,'http://www.tudou.com/albumcover/albumdata/getAlbumItems.html?acode=pEFBZGfERLo&charset=utf-8');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_ENCODING, "gzip");
$output = curl_exec($ch);
curl_close($ch);
$content = json_decode($output);
$content_arr = objtoarr($content);
var_dump($content_arr);