不管文本框是否被点击，我的recaptcha总是返回true

Question

I am trying to validate the recaptcha form on localhost but it is always returning true irrespective of whether I have ticked the checkbox or not. Is this the right behavior?

My form script

<div class="g-recaptcha" data-sitekey="6LeIxAcTAAAAAJcZVRqyHh71UMIEGNQ_MXjiZKhI"></div>

My server

$secret_key = "6LeIxAcTAAAAAGG-vFI1TnRWxMZNFuojJ4WifJWe";
    $request = file_get_contents('https://www.google.com/recaptcha/api/siteverify?secret='.$secret_key.'&response='.$_POST['g-recaptcha-response']);
    $response = json_decode($request);
    var_dump($response->success);
    if($response->success==1){
      echo "Success";
      die();
    }else{
      echo "Fail";
      die();
    }

The keys I am using is default key pair to test with the localhost