why I cannot unset the value of an array(PHP)
<p>I want to unset a field of a two-dimensional array. I got a function like this, but it doesn't work:</p>

<pre><code>  function excludeOldScreeningDate($array){
    foreach($array as $val){
      if($val['ref'] == 'G'){
       unset($val['screening_date']);
      }
    }
    return $array;
  }
</code></pre>
