I'm trying to find a way to pass a custom parameter through paypal's express checkout using NVP. I've tried using the deprecated PAYMENTREQUEST_n_CUSTOM, the supposedly not deprecated PAYMENTREQUEST_0_CUSTOM and the CUSTOM parameters but none of them worked.
The only ways I can see right now (which I'd rather not use) are: 1. use one of the other parameters that I'm not using (like shipping) 2. use the return url and add to it the parameter as a GET parameter 3. use sessions.
According to the error page my version is 92.0. And the rest of the parameters are:
$nvpstr="&SHIPPINGAMT=0&L_SHIPPINGOPTIONNAME0=test&L_SHIPPINGOPTIONAMOUNT0=0&REQCONFIRMSHIPPING=0&NOSHIPPING=1&L_SHIPPINGOPTIONISDEFAULT0=true&ADDRESSOVERRIDE=1$shiptoAddress&".
"&ALLOWNOTE=0&CUSTOM=".$CUSTOM.
"&L_NAME0=".$L_NAME0."&L_AMT0=".$L_AMT0."&L_QTY0=".$L_QTY0.
"&MAXAMT=".(string)$maxamt."&AMT=".(string)$amt."&ITEMAMT=".(string)$itemamt.
"&CALLBACKTIMEOUT=4&CALLBACK=https://www.ppcallback.com/callback.pl&ReturnUrl=".$returnURL."&CANCELURL=".$cancelURL .
"&CURRENCYCODE=".$currencyCodeType."&PAYMENTREQUEST_0_PAYMENTACTION=".$paymentType;