Paypal IPN Detect Refund, PHP
if($_REQUEST["payment_status"] == "refunded"||$testing==1)
{
    $email = $_REQUEST["payer_email"];
    $sid = $_REQUEST["subscr_id"];
    $tid = $_REQUEST["txn_id"];

    if (!$tid)
    {
        $tid='xxx';
    }

    if ($testing==1)
    {
        echo  "testing on";
        $sid = "I-E5E34E0DTMUS";
    }

    $query = "SELECT * FROM idevaff_sales WHERE tid1='$tid'";
    $result = mysql_query($query);
    if (!$result)
    {
        //echo $query; exit;
        mail('***@gmail.com',"1",$query);
    }

    $arr = mysql_fetch_array($result);
    $aid = $arr['id'];

    $query = "SELECT * FROM idevaff_affiliates WHERE tid1='$tid'";
    $result = mysql_query($query);
    if ($result)
    {
        //echo $query;
        mail('***@gmail.com',"2","$query");
    }

    $arr = mysql_fetch_array($result);
    $email = $arr['email'];
    $f_name = $arr['f_name'];

    mail($email,"Affiliate Message - A refund has granted for recent affiliate commission.","Dear $f_name,  nn Message here about refund" );

    $query = "UPDATE idevaff_sales SET approved=3 WHERE tracking='$sid'";
    $result = mysql_query($query);
    if (!$result)
    {
        //echo $query; exit;
        mail('***@gmail.com',"3","$query");
    }
}

if($_REQUEST["payment_status"] == "Refunded" || $_REQUEST["payment_status"] == "Reversed"  || $testing==1)
{
    /*do database work here*/
}