export excel file from mysql data in php

<?php
include 'conn.php';
$sql = "Select * from `emp`";
$result=mysqli_query($con,$sql);

$sep = "\t";
$fp = fopen('report.xls', "w");
$schema_insert = "";
$schema_insert_rows = "";

for ($i = 1; $i < mysqli_num_fields($result); $i++)
{
$schema_insert_rows.= mysqli_fetch_field_direct($result, $i)->name . "\t";
}
$schema_insert_rows.="\n";
echo $schema_insert_rows;
fwrite($fp, $schema_insert_rows);

while($row = mysqli_fetch_row($result))
{
$schema_insert = "";
for($j=1; $j<mysqli_num_fields($result);$j++)
{
if(!isset($row[$j]))
$schema_insert .= "NULL".$sep;
elseif ($row[$j] != "")
$schema_insert .= strip_tags("$row[$j]").$sep;
else
$schema_insert .= "".$sep;
}
$schema_insert = str_replace($sep."$", "", $schema_insert);
$schema_insert = preg_replace("/\r\n|\n\r|\n|\r/", " ", $schema_insert);
$schema_insert .= "\n";
fwrite($fp, $schema_insert);
}
fclose($fp);
?>
<a href="report.xls">Download Export</a>