public_key	The public key field is required.
amount	The amount field is required.
currency	The currency field is required.
details	The details field is required.
custom	The custom field is required.
ipn_url	The ipn url field is required.
success_url	The success url field is required.
cancel_url	The cancel url field is required.
email	The email field is required.
name	The name field is required.