$left_joins .= " left join tt_clients c on (ei.client_id = c.id)";
$sql = "select ei.id, ei.date, ei.client_id, ei.project_id, ei.name, ei.cost, ei.invoice_id $client_field, p.name as project_name
$left_joins .= " left join tt_clients c on (ei.client_id = c.id)";
$sql = "select ei.id, ei.date, ei.client_id, ei.project_id, ei.name, ei.cost, ei.invoice_id $client_field, p.name as project_name