
	 Request keys will contain:

	 receiver_email - echo of 'business' value passed to PayPal
	 item_name - value of 'item_name' as passed to PayPal, or, if not passed, value customer entered
	 item_number - value of 'item_number' as passed to PayPal
	 quantity - value of 'quantity'; either 1 if not customer editable, or value customer entered
	 invoice - value as passed to PayPal
	 custom - value of 'custom' as passed to PayPal; custom is "pass-through" info.


	 payment_status - will be one of the following:
	 completed - transaction approved
	 pending - transaction approval awaits verification; another key will be included: pending_reason; a follow-up notification will be sent when final status is determined
	 failed - payment failed; only happens with payments from a bank account
	 denied - the vendor (you) denied the transaction for some reason


	 pending_reason - reason why the status is 'pending':
	 echeck - customer paid with an echeck
	 intl - you have an intl acct. w/o a withdrawl mechanism; you must manually approve payments
	 verify - you are not yet verified; you must become verified to use IPN
	 address - the customer didn't include a confirmed address && your prefs state that in such a case the approval must be manual
	 upgrade - the payment was made by credit card, but your account needs to be upgraded to Business or Premiere to receive cc payments
	 unilateral - payment was made to an unregistered or unconfirmed e-mail address
	 other - some other reason; you must check with customer service to straighten it out


	 payment_date - Timestamp generated by PayPal; format: "18:30:30 Jan 1, 2000 PST"
         mc_currency - The currency of the transaction
	 mc_gross - amount of transaction before PayPal's fee is subtracted
	 mc_fee - amount of transaction fee (PayPal's cut)
         exchange_rate - exchange rate used if currency exchange service was utilized
	 txn_id - a unique transaction ID generated by PayPal
	 txn_type - either "cart," "web_accept," or "send_money"
	 first_name - customer's first name
	 last_name - customer's last name
	 address_street - customer's street address
	 address_city
	 address_state
	 address_zip
	 address_country
	 address_status - either "confirmed" or "unconfirmed"
	 payer_email - primary e-mail of customer; this should be used for any refunds
	 payer_status - "verified," "unverified," "intl_verified," or "intl_unverified"
	 payment_type - "echeck" or "instant"
	 notify_version - version ofIPN you're using
	 verify_sign - encrypted string sent by PayPal to verify authenticity of transaction; echo it back in the response
	 

	 

When you receive the IPN, you have to echo it back to PayPal in a form post with "&cmd=_notify-validate" appended to the original.

They will respond with a short answer with only the word "VALID" or "INVALID" in the content text.
	 
If it's valid you have to check that the transaction isn't a duplicate.  If it's not and its payment_status is "completed," you can then save and process it however you like.
