<?php $price = "0.00"; if( isset( $_REQUEST[ "price" ] ) ) { $price = $_REQUEST[ "price" ]; } $priceInCents = round( 100 * $price ); $referrer = ""; if( isset( $_REQUEST[ "referrer" ] ) ) { // pass it through without a regex filter // because we can't control its safety in the end anyway // (user can just edit URL sent to FastSpring). $referrer = urlencode( $_REQUEST[ "referrer" ] ); } header( "Location:https://sites.fastspring.com/jasonrohrer/instant/sleepisdeathticket?referrer=$referrer&tags=price_amount=$priceInCents"); ?>