title: PHP http_build_query with two array keys that are same
body: <p>I want to construct this url using http_build_query:</p>
  
  <pre><code>https://www.googleapis.com/freebase/v1/topic/m/0d6lp?filter=/common/topic/notable_for&amp;filter=/common/topic/alias
  </code></pre>
  
  <p>Please note that the "filter=" parameter comes twice in the url, to specify two filters.</p>
  
  <p>I tried to do it this way but having a problem:</p>
  
  <pre><code>$service_url = 'https://www.googleapis.com/freebase/v1/topic';
  $mid = '/m/0d6lp';
  $params = array('filter' =&gt; '/common/topic/notable_for', 'filter' =&gt;   '/common/topic/alias');
  $url = $service_url . $mid . '?' . http_build_query($params);
  </code></pre>
  
  <p>The problem is as 'filter' array key repeats twice, only the last parameter appears in the http_build_query. How do I construct the original url with two filters?</p>