$_SESSION['recent'][] = array(
      'id' => $productimgfolder,
      'title' => $product['Product']['title'],
      'link' => $_SERVER['REQUEST_URI'],
      'image' => 'img/products/'.$productimgfolder.'/'.$product['Product']['mainpicture']
    );
$_SESSION['recent'] = array_slice($_SESSION['recent'],-4);

if(!isset($_SESSION['recent']))
{
        $_SESSION['recent'] = array()
 }

if(!array_key_exists ($productimgfolder, $_SESSION['recent']))
{
    $_SESSION['recent'][$productimgfolder] = array(
          'id' => $productimgfolder,
          'title' => $product['Product']['title'],
          'link' => $_SERVER['REQUEST_URI'],
          'image' => 'img/products/'.$productimgfolder.'/'.$product['Product']['mainpicture']
        );
}