I need my php to post paypal variables

so i have a flash cart component i bought that sends out paypal variables , i just need a correct .php script to receive and email the variables sent .
heres paypals list of variables they use .
https://www.paypal.com/IntegrationCenter/ic_std-variable-reference.html
and this is the sad script im working with now , just to get something to show up :

<?php
$sendTo = "[email protected]";
$subject = "work you bastard";
$message = $_POST["quantity"];
mail($sendTo, $subject, $message, $headers);
?>

obviously nothing is coming up in the message of the email .
thanks a bunch :slight_smile:
-chris