PHP - Problemas Al descargar excel desde php

<?php

/*******EDIT LINES 3-8*******/

$DB_Server = "localhost"; //MySQL Server    

$DB_Username = "pcomp"; //MySQL Username     

$DB_Password = "KneTPuxJ77f4YLNX";             //MySQL Password     

$DB_DBName = "base";         //MySQL Database Name  

$DB_TBLName = "tabla"; //MySQL Table Name   

$filename = "ad";         //File Name

/*******YOU DO NOT NEED TO EDIT ANYTHING BELOW THIS LINE*******/

//create MySQL connection   

$sql = "SELECT * FROM $DB_TBLName";

$Connect = @mysql_connect($DB_Server, $DB_Username, $DB_Password) or die("Couldn't connect to MySQL:<br>" . mysql_error() . "<br>" . mysql_errno());

//select database   

$Db = @mysql_select_db($DB_DBName, $Connect) or die("Couldn't select database:<br>" . mysql_error(). "<br>" . mysql_errno());

//execute query 

$result = @mysql_query($sql,$Connect) or die("Couldn't execute query:<br>" . mysql_error(). "<br>" . mysql_errno());

$file_ending = "xls";

//header info for browser

header("Content-Type: application/xls");

header("Content-Disposition: attachment; filename=$filename.xls");

header("Pragma: no-cache");

header("Expires: 0");

/*******Start of Formatting for Excel*******/

//define separator (defines columns in excel & tabs in word)

$sep = "\t"; //tabbed character

//start of printing column names as names of MySQL fields

for ($i = 0; $i < mysql_num_fields($result); $i++) {

echo mysql_field_name($result,$i) . "\t";

}

print("\n");

//end of printing column names  

//start while loop to get data

    while($row = mysql_fetch_row($result))

    {

        $schema_insert = "";

        for($j=0; $j<mysql_num_fields($result))

        {

            if(!isset($row[$j]))

                $schema_insert .= "NULL".$sep;

            elseif ($row[$j] != "")

                $schema_insert .= "$row[$j]".$sep;

            else

                $schema_insert .= "NULL".$sep;

        }

        $schema_insert = str_replace($sep."$", "", $schema_insert);

       // $schema_insert = preg_replace("/\r\n|\n\r|\n|\r/", " ", $schema_insert);

        $schema_insert .= "\n";

        print(trim($schema_insert));

        print "\r";

    }

?>