title: "missingRequiredParameter" error when interacting with YouTube API
body: <p>When I use your curl method of YouTube API (v3)  </p>
  
  <pre><code>$api_key = 'YOUR_API_KEY';
  $url = 'https://www.googleapis.com/youtube/v3/channels?part=snippet,statistics&amp;key=' . $api_key . '&amp;forUsername=' . $_GET['username'];
  
  // initializes the request
  $curl = curl_init();
  // sets the url
  curl_setopt($curl, CURLOPT_URL, $url);
  
  // enables that curl_exec() returns content instead of status code
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
  
  // allows redirects
  curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1);
  
  // checks if a secure site has been requested
  if(preg_match('/^https:\/\//', $url)){
      // if so, verification is disabled
      curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
      curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
  }
  // performs the actual request
  $data = curl_exec($curl);
  // destructs the request
  curl_close($curl);
  
  // this line converts the json string which is returned into a php object
  $data = json_decode($data);
  print_r($data);
  </code></pre>
  
  <p>It shows </p>
  
  <pre><code>Array ( 
      [error] =&gt; Array (
          [errors] =&gt; Array (
              [0] =&gt; Array (
                  [domain] =&gt; youtube.parameter 
                  [reason] =&gt; missingRequiredParameter 
                  [message] =&gt; No filter selected. 
                  [locationType] =&gt; parameter 
                  [location] =&gt; 
              ) 
          )
          [code] =&gt; 400 
          [message] =&gt; No filter selected. 
      ) 
  )
  </code></pre>
  
  <p>Why this error is coming up?</p>