ZenCart is just a shopping cart, you still need to integrate a payment processor into ZenCart in order to process payment. Such payment processor includes PayPal, Authorize.net, and LinkPoint.
In this article will are going to talk about integrating PayPal as the payment processor into ZenCart. In particular, there are two PayPal services that are suitable for integration: (a) Paypal Website Payment Standard, and (b) PayPal Website Payment Pro. Let's look at the two choices more carefully.
Customer interactions such as "add to cart", "view cart", "update quantity", "remove from cart", "track order", "billing address input", "shipping address input" all happens on your own website.
At the very last step of the checkout process, the customer is directed to a PayPal-hosted page for credit card entry.
Once the customer enters their credit card on the PayPal hosted page or use their PayPal account, they will then be redirected back to your website's thank you page. Your customer will then immediately receive two emails. One is the order confirmation sent by Zencart. The second email is sent by PayPal indicating to the customer that they had sent money to the merchant.
Because the customer's credit card entry happens on a PayPal-hosted page, the merchant do not bear the responsibility of PCI Compliance (Payment Card Industry Compliance). It also means that you do not need to secure your website with SSL encryption. Credit card numbers are not accessible to you and they are not stored on your website or your webhost.
As of this writing, PayPal does not charge any monthly fees for Website Payment Standard. See Paypal overview here for more details (see "option 2 Third-Party Carts" for the option for integration with ZenCart). See this tutorial on how to integrate PayPal Website Payment Standard with ZenCart.
Paypal Website Payment Pro is different from Website Payment Standard in that for Payment Pro, the last step of the checkout process, credit card input happens right on your website instead of on the PayPal-hosted page. Because credit card input happens directly on the merchant's website, the merchant bears a greater burden in terms of PCI compliance. The merchant must secure website with SSL encryption by purchasing an SSL certificate from webhost. That ensures that credit card number transmission is done via secured HTTPS instead of non-secured HTTP.
As of this writing, Paypal charges a monthly fee for Website Payment Pro (see details on PayPal site).
Note that even with this option, Paypal still requires a "PayPal Express Checkout" button on merchant site. Page 13 - 14 of the PayPal Website Payment Pro Integration Guide says ...
"Website Payments Pro must be integrated on your website in the following ways. You should:
1. Present the PayPal Express Checkout button and associated messaging before requesting
shipping address, billing address, and financial information. PayPal account holders should
not be required enter any of this information on your website, because the information is
available from their PayPal accounts.
2. Display PayPal as an option along side other payment methods, wherever other payment
methods are offered.
3. Present the PayPal mark graphic wherever other payment marks are displayed."
See PayPal's comparison here. The big difference is that for Website Payment Pro, you are paying monthly to PayPal; whereas there is no monthly fee for Website Payment Standard.
For small merchants just starting out, Website Payment Standard may be easier to maintain positive cash flow because there is no PayPal monthly fees. Merchants only pay the usual PayPal transaction fees whenever there is a sale. For Website Payment Pro, merchants must pay the PayPal monthly fee even if they have no sales. When volume of business expands, merchants can always upgrade to Website Payment Pro in order to provide a more professional user experience.
Another disadvantage of Website Payment Pro is that the merchant has a greater burden in term of PCI compliance.
