title: Why get this notice in PHP
body: <blockquote>
    <p>Notice: Only variables should be passed by reference in
    C:\xampp\htdocs\PHP\processor.php on line 43</p>
    
    <p>Line 43 is: $extension = end(explode(".",
    strtolower($_FILES['photoUpload']['name'])));</p>
  </blockquote>
  
  <pre><code>$allowedExts = array( "gif", "jpeg", "jpg", "png" );
  $extension = end(explode(".", strtolower($_FILES['photoUpload']['name'])));
  
  $allowedType = array( "image/gif", "image/jpeg", "image/jpg", "image/png" );
  
  if( !in_array($_FILES['photoUpload']['type'], $allowedType) )
  die ("&lt;br&gt;Unsupported file type!");
  
  if( !in_array($extension, $allowedExts) )
  die ("&lt;br&gt;Unsupported file extension!");
  </code></pre>