Warning: Cannot modify header information - headers already sent by (output started at

ทำตามคำแนะนำแล้วยังใช้ไม่ได้ครับ
ขอบคุณครับ

เพิ่มเติมครับ
<?
$connection=mysql_connect("localhost","***"****,"") or die("เชื่อมต่อฐานข้อมูลไม่ได้");
mysql_select_db("*****") or die("ไม่สามารถเลือกฐานข้อมูลได้");
$q="select * from ****";
$qr=mysql_query($q);
$row_num=mysql_num_rows($qr);
$col_arr=array("Auto_ID","qq","ww","aa","pp");
$col_num=count($col_arr);
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");;
header("Content-Disposition: attachment;filename=data.xls ");
?>
<?php echo '<?xml version="1.0" encoding="utf-8"?>'; ?>

<?php echo'<?mso-application progid="Excel.Sheet"?>';?>

<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:x="urn:schemas-microsoft-com:office:excel"
xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<Styles>
<Style ss:ID="Default" ss:Name="Normal">
<Alignment ss:Vertical="Bottom"/>
<Borders/>
<Font x:CharSet="222"/>
<Interior/>
<NumberFormat/>
<Protection/>
</Style>
</Styles>
<Worksheet ss:Name="ข้อมูล">
<Table ss:ExpandedColumnCount="<?=$col_num?>" ss:ExpandedRowCount="<?=$row_num+1?>" x:FullColumns="1"
x:FullRows="1">
<Row>
<?php foreach($col_arr as $key=>$value){ ?>
<Cell><Data ss:Type="String"><?=$value?></Data></Cell>
<?php } ?>
</Row>
<?php
while($rs=mysql_fetch_array($qr)){
?>
<Row>
<Cell><Data ss:Type="Number"><?=$rs['Auto_ID']?></Data></Cell>
<Cell><Data ss:Type="String"><?=$rs['qq']?></Data></Cell>
<Cell><Data ss:Type="String"><?=$rs['ww']?></Data></Cell>
<Cell><Data ss:Type="String"><?=$rs['aa']?></Data></Cell>
<Cell><Data ss:Type="String"><?=$rs['pp']?></Data></Cell>
</Row>
<?php } ?>
</Table>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<Selected/>
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
</Workbook>