Hi, I am new for php developing, here i enclosed my export excel some data from db using php code its working in localhost well but after deploying server its not working ? this is my php code

<?php
session_start();
if(!isset($_SESSION['branch']))
{
header("location:logout.php");
}

include('db.php');
include('excelwriter.calss.php');
// GET FROM Monthly Overall Report.php
$branch=$_REQUEST['branch'];
$atoms = explode('-',$_REQUEST['month']);
$year = $atoms[1];
$month = $atoms[0];
$totalamt="";
$totalbal="";
?>
<html><head><title>JAI SAIRAM ASSOCIATES</title>
<script language="javascript">
function download()
{
window.location='report.xls';
}
</script>
</head>
<body alink="#2046EE" link="#2046EE">

</head>
<body>
<form name="monthly_customer_reportview" method="post" enctype="multipart/form-data">
<center>
<font face="Arial, Helvetica, sans-serif" size="2">
<h1>JAI SAIRAM ASSOCIATES</h1>
<h2>Monthly Customer Report</h2>
<h4>Month: &nbsp;<?php echo $month; ?>&nbsp;-&nbsp;<?php echo $year; ?>&nbsp;&nbsp;&nbsp;&nbsp;Branch:&nbsp;&nbsp;<?php echo $branch; ?></h4>
</font>
</center>

<?php
/* Fetch Using Branach And Month-Year */

if(isset($_REQUEST["month"])){
?>
<table align="center" width="98%" border="1" cellspacing="0" cellpadding="1" >
<tr><b>
<th>Name</th>
<th>Mobile</th>
<th>Policy</th>
<th>Branch</th>
<th>PolicyAmount</th>
<th>MedicalAmount</th>
<th>PaidAmount</th>
<th>Balance</th>
<th>Manager</th>
<th>Sales Rep</th>
<th>Telecaller</th>
</b>
</tr>
</tr>
<?php
$excel=new ExcelWriter("report.xls");
if($excel==false)
echo $excel->error;
$myArr=array("SNO","NAME","MOBILE","POLICY","BRANCH","TOTAL AMOUNT","MEDICAL AMOUNT","AMOUNT PAID","BALANCE","TO MANAGER","SALES REP","TELECALLER");
$excel->writeLine($myArr);

$sel_cust=mysql_query("SELECT a.name,a.cust_id,a.mobile,a.policy,a.branch,a.total_amount,a.telecaller,a.manager,a.sales_rep,a.medi cal_amount,b.amount_paid,
a.balance FROM customer_history a INNER JOIN (SELECT cust_id,SUM(installamt) as amount_paid FROM
customer_installment_history WHERE MONTHNAME(paid_date)='$month' AND year(paid_date)='$year' AND branch='$branch'
GROUP BY cust_id) b on a.cust_id=b.cust_id GROUP BY a.cust_id")or die("Query failed".mysql_error()."actual".$sel_cust);
$count = mysql_num_rows($sel_cust);
if($count> 0){
if($sel_cust!=false){ $i=1;
while($sel_row = mysql_fetch_array($sel_cust)){
$totalamt+=$sel_row['amount_paid'];
$totalbal+=$sel_row['balance'];
$myArr=array($i,$sel_row['name'],$sel_row['mobile'],$sel_row['policy'],$sel_row['branch'],$sel_row['total_amount'],$sel_row['medical_amount'],$sel_row['amount_paid'],$sel_row['balance'],$sel_row['manager'],$sel_row['sales_rep'],$sel_row['telecaller']);
$excel->writeLine($myArr);
$i++;
?>
<tr>
<td align="center"><?php echo $sel_row['name']; ?></td>
<td align="center"><?php echo $sel_row['mobile']; ?></td>
<td align="center"><?php echo $sel_row['policy']; ?></td>
<td align="center"><?php echo $sel_row['branch']; ?></td>
<td align="center"><?php echo $sel_row['total_amount']; ?></td>
<td align="center"><?php echo $sel_row['medical_amount']; ?></td>
<td align="center"><?php echo $sel_row['amount_paid']; ?></td>
<td align="center"><?php echo $sel_row['balance']; ?></td>
<td align="center"><?php echo $sel_row['manager']; ?></td>
<td align="center"><?php echo $sel_row['sales_rep']; ?></td>
<td align="center"><?php echo $sel_row['telecaller']; ?></td>


</tr>
<?php
}
}else{
?>
<tr><td colspan="11" align="center">No Records Found</td></tr>
<?php
} ?><tr><td colspan="11" align="center"><b>Total CollectionAmount:<?php echo $totalamt; ?>Total Balance:<?php echo $totalbal; ?></td></b></tr>
</table>
<?php } }?><br>

<div align="right"><h3><a href="#" a onClick="javascriptrint()">Print Page</a>&nbsp;*&nbsp;<a href="javascript:void(0);" onClick="download();" >Download Excel Report</a></h3>
</div>
</form>
</body>
</html>