如何从json数组中删除其他标记？

Question

当我尝试从wordpress网站获取数据时，我得到了额外的条款。

    function get_data($url)
    {
      $ch = curl_init();
      $timeout = 20;
      curl_setopt($ch,CURLOPT_URL,$url);
      curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
      curl_setopt($ch,CURLOPT_CONNECTTIMEOUT,$timeout);
      $data = curl_exec($ch);
      curl_close($ch);
      return $data;
    }

$uname=$_GET['uname'];
$pwd=$_GET['pwd'];

    $root_url = "http://domain.com/";
    $nonce_url = $root_url."api/get_nonce/?controller=auth&method=generate_auth_cookie";
    $json = get_data($nonce_url);
    $json_data =  json_decode(substr($json,3), true);

    // check that user is logged into WP
    $nonce = $json_data['nonce']; // need to have an exception handler in case this fails

echo $json;

，输出为，

    {"status":"ok","controller":"auth","method":"generate_auth_cookie","nonce":"3ca4ad3a80"}

如何从json数组中删除ï？¿这个额外的术语？