title: Insert just the array key without value
body: <p>I have the following code in PHP:</p>
  
  <pre><code>$keys = array('a', 'b', 'c');
  $data = array();
  $data[0] = array_fill_keys($keys,'');
  </code></pre>
  
  <p>After some follow-up code, when the array set is empty, it returns:</p>
  
  <pre><code>a,b,c
  ,,,
  </code></pre>
  
  <p>I've slimmed down to the problem is <code>$data[0] = array_fill_keys($keys,'');</code></p>
  
  <p>What can I do to have the result as:</p>
  
  <pre><code>a,b,c
  </code></pre>
  
  <p>Thanks.</p>