code: function TbsSheetSlide_DeleteDisplay($id_or_name, $ok, $delete) {
  
  		if (is_null($ok)) $ok = true; // default value
  
  
  		$ext = $this->ExtEquiv;
  
  		$ok = (boolean) $ok;
  		if (!is_array($id_or_name)) $id_or_name = array($id_or_name);
  
  		foreach ($id_or_name as $item=>$action) {
  			if (!is_bool($action)) {
  				$item = $action;
  				$action = $ok;
  			}
  			$item_ref = (is_string($item)) ? 'n:'.htmlspecialchars($item) : 'i:'.$item; // help to make the difference beetween id and name
  			if ($delete) {
  				if ($ok) {
  					$this->OtbsSheetSlidesDelete[$item_ref] = $item;
  				} else {
  					unset($this->OtbsSheetSlidesVisible[$item_ref]);
  				}
  			} else {
  				$this->OtbsSheetSlidesVisible[$item_ref] = $ok;
  			}
  		}
  
  	}
docs: Delete or Display a Sheet or a Slide according to its numbre or its name
  @param $id_or_name Id or Name of the Sheet/Slide
  @param $ok         true to Keep or Display, false to Delete or Hide
  @param $delete     true to Delete/Keep, false to Display/Hide