Page Protection

I've had a difficult ti开发者_StackOverflow社区me working with PayPal express checkout... Basically I'm looking to protect a PAGE, not a download or anything. The user pays and they can access that page one time. And have to pay each time they want to access the page.

Does anyone have a simple PHP solution to protect my page until the person pays through PayPal? Or even a pre-written example of the PayPal code for Digital Goods for Express Checkout?

Thanks in advance.

---

PayPal doesn't have much to do with this -- it's all about the logic you place on your 'return page' (the page the buyer returns to after they have completed payment).

For a simple Express Checkout integration you would:
1. Call the SetExpressCheckout API
2. Supply the AMT, RETURNURL and CANCELURL
3. Retrieve the token as returned in the SetExpressCheckout response.
4. Redirect the buyer to https://www.paypal.com/cgi-bin/webscr?cmd=_express-checkout&token=EC-xxxtoken-herexxx&useraction=commit
5. When the buyer agrees to the payment and is returned back to your RETURNURL, call the GetExpressCheckoutDetails API and supply the token to retrieve the PayerID (alternatively; the token is also appended in the GET array for your RETURNURL)
6. Call DoExpressCheckoutPayment to finalize the payment.
7. Now that the payment is complete, do whatever logic you have to to ensure the transaction is completed and provide the buyer access to the content you wish him/her to see (could be the RETURNURL page itself, or a completely different page).

Sample (NVP) API calls would look similar to the following:

1. SetExpressCheckout Request METHOD=SetExpressCheckout&USER=yourAPIuser&PWD=yourAPIpwd&SIGNATURE=yourAPIsig&VERSION=78.0&AMT=0.01&RETURNURL=http://www.your-return-url.com/&CANCELURL=http://www.cancelurl.com/

2. SetExpressCheckout Response ......
   Ack=Success
   TOKEN=EC-12345678 .......

3. GetExpressCheckoutDetails Request
   METHOD=SetExpressCheckout&USER=yourAPIuser&PWD=yourAPIpwd&SIGNATURE=yourAPIsig&VERSION=78.0&TOKEN=EC-12345678

4. GetExpressCheckoutDetails Response
   .....
   Ack=Success
   PAYERID=ABCDEFGH
   ......

5. DoExpressCheckoutPayment Request METHOD=SetExpressCheckout&USER=yourAPIuser&PWD=yourAPIpwd&SIGNATURE=yourAPIsig&VERSION=78.0&AMT=0.01&PAYERID=ABCEDFGH&TOKEN=EC-12345678

6. DoExpressCheckoutPayment Response
   ....
   Ack=Success
   PAYMENTSTATUS=Completed
   ....

See also SetExpressCheckout: https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_r_SetExpressCheckout
GetExpressCheckoutDetails: https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_r_GetExpressCheckoutDetails
DoExpressCheckoutPayment: https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_r_DoExpressCheckoutPayment

As well as https://www.x.com/ > API Reference.

Note: I'm using "useraction=commit" in the redirect URL to PayPal because that will change the 'Continue' button on the PayPal 'Review Your Payment' to a 'Pay now' button. Thus implying the buyer will be immediately charged as soon as he clicks on that button. It's just handy.