Modify Checkout Amount

It is for current members/subscribers wishing to upgrade their subscription level. We are using the modify form to handle the change in membership level and that works fine. I just need to be able to apply a discount according to how much the member has already paid and how far through that payment period they are.

So, it’s not a matter of changing the shortcode since the amount is going to be different for each member. The modification form has the same prices as the registration form, it’s a matter of applying the appropriate discount for each member when they apgrade.

Thank you! This thread has been hugely helpful.

FYI for anyone else who might benefit. The above payflow_get_profile method gave me everything I needed except the last payment amount to calculate the appropriate prorated amount. I found it with a combo of the payflow_get_profile method and a parameter I found in the Payflow recurring billing guide:

$payflow["TRXTYPE"] = "R";
$payflow["ACTION"] = "I";
$payflow["TENDER"] = "C";
$payflow["PAYMENTHISTORY"] = "O";
$payflow["ORIGPROFILEID"] = $subscr_id;

if(($profile = c_ws_plugin__s2member_paypal_utilities::paypal_payflow_api_response($payflow)) && empty($profile["__error"]))
	print_r($profile);

Returns all the payments in the profile.

If I could get some more help on this I would greatly appreciate it. I got all the calculations sorted out and pass the appropriate discount amount to the form via query in the URL, which is then added to the checkout form as a hidden field:
<input type="hidden" id="s2-custom-pro-rate-amt" name="s2_custom_pro_rate_amt" value="<?php echo $_GET["amt"]; ?>" />

My function to subtract the discount from the total was not working. Although I just spotted an error so maybe it is working now… I have never had much luck getting the PayPal sandboxes working, particularly with Payflow, which we’re using on the site in question. Can you suggest a suitable way to test this code? I tried just viewing the results of the form submission, but most of it was encrypted.

If you want to test it directly you could just change $disc = bd_pro_rate_amount(); to $disc = 20; or some other fixed amount. I am using the same function that produces the discount amount for the query string so that no wise guys cotton on to the discount in the URL and game the system.

add_filter("ws_plugin__s2member_pro_paypal_checkout_post_attr", "bd_paypal_pro_checkout_form_attr");
function bd_paypal_pro_checkout_form_attr($attr = array()) {
	if (isset($_POST["s2_custom_pro_rate_amt"])) {
		$disc = bd_pro_rate_amount();
		if($_POST["s2_custom_pro_rate_amt"] > 0 && isset($attr["ta"])) {
			if ($attr["ta"] > $disc)
				$attr["ta"] = $attr["ta"] - $disc;
			else
				$attr["ta"] = 0;
		}
		elseif($_POST["s2_custom_pro_rate_amt"] > 0 && !isset($attr["ta"])) {
			if ($attr["ra"] > $disc)
				$attr["ta"] = $attr["ra"] - $disc;
			else
				$attr["ta"] = 0;

			$attr["tt"] = "Y";
			$attr["tp"] = 1;
		}
	}
	return (array) $attr;
}