Integrate Paypal Express Checkout Solution

As a web developer, there will surely be someday where you wish to integrate Paypal into one of your products or services. The most appropriate way is to read the documentation provided by Paypal. But reading it doesn't mean you will understand the documentation with one shot and this call for a lot of research and finding before your Paypal will work. I went through this process these few days that is why there wasn't much article written in the process.  Although it wasn't really difficult but going through the process of reading first before looking into their sample codes really wasn't the correct way of approaching this solution. Instead, looking into the sample code will definitely brings light to integrating Paypal express checkout solution (well, you still have to read a bit). In this article, i will try to demonstrate Paypal express checkout solution as simple as possible for you guys to be able to DIY.

Paypal Express Checkout

What is Paypal Express checkout solution? Paypal Express Checkout makes it easier for your customers to pay and allows you to accept PayPal while retaining control of the buyer and overall checkout flow. This means that you can integrate a payment solution with Paypal that retain most of the interaction on your website other than user login and verifying the product they are purchasing. Paypal express checkout also provides you with the ability to create recurring payment which can really eliminate the need to repurchase the exact service or product every single time. However, Paypal express checkout solution doesn't have the ability to allow your user to use credit card for purchases. Your customers must have Paypal in order to purchase with this solution. Credit card solution will only be available together with Paypal in Website Payment Pro solution. Hopefully this clear some doubt and help you select what solution you really need.

Integrate Paypal Express Checkout Solution - Step 1

Firstly, you might wonder where exactly are the correct documentation out of all the places in Paypal. You can get the documentation and Sample at the respective links. The sample is contain at the section PayPal API: Name-Value Pair Interface as i believe this will give you a better understanding on the flow of Paypal express check out solution. The sample files will required you to throw them  into your server and run (go to the browser and key in the url you have thrown the folder into) as it will simulate some of the payment flow you might want. Then you will look into the code and see how they are achieved. Please take note that localhost might not work for you as it will required you to have curl installed.

Integrate Paypal Express Checkout Solution - Step 2

Once the sample are placed into your server and you have play around, the next thing you might wonder is the exact file you will required to run your own Paypal express checkout solution. And here are the files you will only need.

  • APIError - display error
  • CallerService - main player that initial the talk
  • constants - all the required variables
  • SetExpressCheckout - display for step 1 of the process
  • GetExpressCheckoutDetails - display for step 2 of the process
  • DoExpressCheckoutPayment -  display for step 3 of the process + send final request to paypal
  • ReviewOrder - request handler for step 1 and responsible to redirect to step 2

The files i am looking at are all PHP files.  Well, the above file respective function should be self explained. The first 3 files(APIError, CallerService and Constants) are the files imported into the ReviewOrder and  DoExpressCheckoutPayment files as they are required to talk to Paypal. Once we understand this it is time to go into a more complicated stuff.

Integrate Paypal Express Checkout Solution - Step 3

To illustrate what is going on in the sample file, we will look at the following diagram provided by Paypal.

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