Exporting mysql database table to Excel with respect to query provided

<?php
/*******EDIT LINES 3-8*******/
$DB_Server = "localhost"; //MySQL Server  
$DB_Username = "root"; //MySQL Username    
$DB_Password = "pass";             //MySQL Password    
$DB_DBName = "p2p-pro2013-2014";         //MySQL Database Name
$DB_TBLName = "tbl_student_register"; //MySQL Table Name  
$filename = "student_list";         //File Name

/*******YOU DO NOT NEED TO EDIT ANYTHING BELOW THIS LINE*******/  
//create MySQL connection  
$sql = "select rollno as 'Roll No.', stud_fname as 'First Name', stud_mname as 'Middle Name', stud_lname as 'Last Name' 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 the 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);$j++)
        {
            if(!isset($row[$j]))
                $schema_insert .= "NULL".$sep;
            elseif ($row[$j] != "")
                $schema_insert .= "$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);
        $schema_insert .= "\t";
        print(trim($schema_insert));
        print "\n";
    }  
?>