title: reCaptcha: error code "invalid-keys"
body: <p>I currently implementing the reCaptcha for an form with HTML and PHP. The client-side solution works without any problems. But the server side fails with the validation.</p>
  
  <p>So here is my server side code:</p>
  
  <pre><code>$data = array(
      "secret" =&gt; "MY_SECRET_KEY",
      "response" =&gt; $captcha_response,
      "remoteip" =&gt; $_SERVER['REMOTE_ADDR']
  );
  $opts = [
      "http" =&gt; [
          "method" =&gt; "POST",
          "header" =&gt; "Accept-language: en",
          "content" =&gt; http_build_query($data)
      ]
  ];
  
  $context = stream_context_create($opts);
  
  $data = json_decode(file_get_contents('https://www.google.com/recaptcha/api/siteverify', false, $context), true);
  </code></pre>
  
  <p>So now when I dump the result I get the following output:</p>
  
  <pre><code>array(4) {
    ["success"]=&gt;
    bool(false)
    ["challenge_ts"]=&gt;
    string(20) "2017-06-22T13:14:50Z"
    ["hostname"]=&gt;
    string(9) "localhost"
    ["error-codes"]=&gt;
    array(1) {
      [0]=&gt;
      string(12) "invalid-keys"
    }
  }
  </code></pre>
  
  <p>I'm sure that the response code will completly send to the PHP script.</p>
  
  <p>I also searched in the API docs, but only find these <a href="https://developers.google.com/recaptcha/docs/verify#error-code-reference" rel="noreferrer">error codes</a> and nothing matches with <code>invalid-keys</code>.</p>
  
  <p>What did I wrong?</p>