$left_joins .= " left join tt_users u on (u.id = ei.user_id)";
if ($report['show_client'] || 'client' == $group_by_option)
$left_joins .= " left join tt_clients c on (c.id = ei.client_id)";
if ($report['show_project'] || 'project' == $group_by_option)
$left_joins .= " left join tt_projects p on (p.id = ei.project_id)";
$left_joins .= " left join tt_users u on (u.id = ei.user_id)";
if ($report['show_client'] || 'client' == $group_by_option)
$left_joins .= " left join tt_clients c on (c.id = ei.client_id)";
if ($report['show_project'] || 'project' == $group_by_option)
$left_joins .= " left join tt_projects p on (p.id = ei.project_id)";