Need some help

[lmf]

I want to make something like this

http://domain.com/downloads.php?id=p...&serial=123456

in one php page

<?php
if ($id === 'productname'){
    $link = mysql_pconnect("localhost", "root", "password"); 
    mysql_select_db("dbname") or die("Database Error."); 
    $query ="SELECT name, email, serial FROM info WHERE serial = '" . $_GET["serial"]. "'"; 
    $result = mysql_query($query) or die ("Database Error." . mysql_error( )); 

    if ( mysql_num_rows($result) == 0 ) {
        echo "Not Found Serial Match";
        or die(mysql_error()); 
        mysql_close($link); 
        exit;
    }

    while ($row = mysql_fetch_row($result)) { 
        echo "Found Serial";
    } 

    mysql_free_result($result); 
    mysql_close($link); 
}
    ?>

Thank you for your help