I need to enable a custom field when PayPal notifies me of a payment. I am trying to use advanced variables, but I see no way that I can make them dynamic.
Pretend that I have a "xyzzy" field with the value "plugh". I would like PayPal to include form.xyzzy = plugh with all the other fields that it sends to my notify_url.
Of course, the xyzzy value may be "foo", depending on what they want.
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