I prefer whenever possible to have no warnings and no erros in the code so I run with:

Code:
error_reporting(E_ALL);
When I do that, I see the following error:

PHP Notice: Undefined variable: show_search_header in \includes\modules\sideboxes\search_header.php on line 19

The simple solution is to change this:
Code:
if ($search_header_status->RecordCount() != 0) {
    $show_search_header= true;
}
to this:

Code:
$show_search_header = false;

if ($search_header_status->RecordCount() != 0) {
  $show_search_header= true;
}