GridConnector error exportingo to excel

Hello,
I m trying to export my grid to excel in server side way , and i m getting this error at my excel file.

My code

<?php require("../../Obj/Connector/codebase/grid_config.php"); require("../../Obj/Connector/codebase/db_oracle.php"); require("../../Obj/Connector/codebase/grid_connector.php"); require("../../Obj/Connector/codebase/convert.php"); $res= oci_connect('sisengweb', 'sisengweb', 'homolog'); $convert = new ConvertService("localhost/generate.php"); $convert->excel('teste.xls',true); $grid = new GridConnector($res,"Oracle"); $grid->dynamic_loading(50000); $grid->render_sql("SELECT * FROM ITENS_ORCAMENTO where ITOR_EPRD_COD = 'VA025' AND ITOR_TIPO_ITEM = 'CAMO'", "ITOR_COD","ITOR_COD,ITOR_DESC,ITOR_UNIM_SIG,ITOR_CUSTO_UNIT_SENC,ITOR_PERC_ENCARGOS, ITOR_FATOR_MO,ITOR_CUSTO_UNIT_ITEM,ITOR_QTD_HRS_PADRAO_MES,ITOR_MOOR_SIG,ITOR_GRPR_COD,ITOR_TPIN_COD,ITOR_COND_PAGTO"); ?>

Any idea??

I solve it,
The header configuration is mandatory.

Falowwwwww