Cant get the table column in the .xls file - php

Question

I have a page that allow user to export particular data in .xls file.
Here is the code.
if(isset($_SESSION['name'])){
$user_name=$_SESSION['name'];$sql = "select * from asset_details inner join bank_details on asset_details.user_id=bank_details.user_id inner join merchant_details on asset_details.user_id=merchant_details.user_id inner join merchant_status on asset_details.user_id=merchant_status.user_id inner join merchant_ids on asset_details.user_id=merchant_ids.user_id inner join terminal_details on asset_details.user_id=terminal_details.user_id where asset_details.user_id='$user_name' order by merchant_details.time_date asc" ; $result = mysqli_query($db,$sql); function filterData(&$str)
{
$str = preg_replace("/\t/", "\\t", $str);
$str = preg_replace("/\r?\n/", "\\n", $str);
if(strstr($str, '"')) $str = '"' . str_replace('"', '""', $str) . '"';
}
// file name for download
$fileName = "report" . date('Ymd') . ".xls";
// headers for download
header("Content-Disposition: attachment; filename=\"$fileName\"");
header("Content-Type: application/vnd.ms-excel");
$flag = false;
foreach($result as $row) {
if(!$flag) {
// display column names as first row
echo implode("\t", array_keys($row)) . "\n";
$flag = true;
}
// filter data
array_walk($row, 'filterData');
echo implode("\t", array_values($row)) . "\n";
}
exit;}
The Problem is that while exporting the data it takes column name from database rather than from the column name on the page.