PayPal IPN Listener

A PayPal IPN (Instant Payment Notification) listener for PHP

Index

• Prerequisites
• Installation
• Architecture
• Usage
• Extending
• Notes

Prerequisites

1. PHP >=7.1.0
2. A good understanding of how the PayPal Instant Payment Notification system works (see here)

Installation

composer require mike182uk/paypal-ipn-listener

Architecture

This package is made up of several components that work together:

• Listener - Listens for and processes the IPN messages
• Verifier - Verifies the IPN message with PayPal
• Service - Communicates with PayPal
• Message - Wrapper around the IPN message
• MessageFactory - Creates a new message instance from a data source
• EventDispatcher - Dispatches events

The listener creates a Message using a MessageFactory. The Message is passed to the Verifier which uses a Service to communicate with PayPal. The Listener uses the EventDispatcher to dispatch events relating to the outcome of the IPN message verification.

The MessageFactory and Service components are swappable components.

This package provides 2 message factories:

1. Mdb\PayPal\Ipn\MessageFactory\InputStreamMessageFactory - Creates a message from the php://input stream
2. Mdb\PayPal\Ipn\MessageFactory\ArrayMessageFactory - Creates a message from an array passed to the setData method

This package provides 1 service:

1. Mdb\PayPal\Ipn\Service\GuzzleService - Uses Guzzle to communicate with PayPal

Usage

You can either build up the listener object manually or you can use a listener builder. This package provides 2 listener builders:

1. Mdb\PayPal\Ipn\ListenerBuilder\Guzzle\InputStreamListenerBuilder - Builds a listener using the guzzle service and the input stream message factory
2. Mdb\PayPal\Ipn\ListenerBuilder\Guzzle\ArrayListenerBuilder - Builds a listener using the guzzle service and the array message factory

Using a listener builder is the preferred way of building up a listener object.

Using a listener builder

use Mdb\PayPal\Ipn\ListenerBuilder\Guzzle\InputStreamListenerBuilder as ListenerBuilder;

$listener = (new ListenerBuilder)->build();

Building up the listener manually

use GuzzleHttp\Client;
use Mdb\PayPal\Ipn\InputStream;
use Mdb\PayPal\Ipn\Listener;
use Mdb\PayPal\Ipn\MessageFactory\InputStreamMessageFactory;
use Mdb\PayPal\Ipn\Service\GuzzleService;
use Mdb\PayPal\Ipn\Verifier;
use Symfony\Component\EventDispatcher\EventDispatcher;

$service = new GuzzleService(
    new Client(),
    'https://www.sandbox.paypal.com/cgi-bin/webscr'
);

$verifier = new Verifier($service);

$messageFactory = new InputStreamMessageFactory(new InputStream());

$listener = new Listener(
    $messageFactory,
    $verifier,
    new EventDispatcher()
);

A lot of plumbing is needed to create the listener manually. The job of the listener builder is to abstract away this logic.

Subscribing to events

Once you have created the listener object you can subscribe to the events that it will dispatch:

use Mdb\PayPal\Ipn\Event\MessageVerifiedEvent;
use Mdb\PayPal\Ipn\Event\MessageInvalidEvent;
use Mdb\PayPal\Ipn\Event\MessageVerificationFailureEvent;

$listener->onVerified(function (MessageVerifiedEvent $event) {
   $ipnMessage = $event->getMessage();
   
   // IPN message was verified, everything is ok! Do your processing logic here...
});

$listener->onInvalid(function (MessageInvalidEvent $event) {
   $ipnMessage = $event->getMessage();
   
   // IPN message was was invalid, something is not right! Do your logging here...
});

$listener->onVerificationFailure(function (MessageVerificationFailureEvent $event) {
    $error = $event->getError();
    
    // Something bad happend when trying to communicate with PayPal! Do your logging here...
});

You can use any callable when subscribing to an event:

class IpnProcessor
{
    public function onVerified(MessageVerifiedEvent $event)
    {
        $message = $event->getMessage();
        
        // ...
    }
}

$listener->onVerified(array(new IpnProcessor, 'onVerified'));

class IpnProcessor
{
    public static function onVerified(MessageVerifiedEvent $event)
    {
        $message = $event->getMessage();
        
        // ...
    }
}

$listener->onVerified(array('IpnProcessor', 'onVerified'));

Listening for IPN messages

The last thing you need to do to kick of the process is listen for an IPN message:

$listener->listen();

Full Example

use Mdb\PayPal\Ipn\Event\MessageVerifiedEvent;
use Mdb\PayPal\Ipn\Event\MessageInvalidEvent;
use Mdb\PayPal\Ipn\Event\MessageVerificationFailureEvent;
use Mdb\PayPal\Ipn\ListenerBuilder\Guzzle\InputStreamListenerBuilder as ListenerBuilder;

$listener = (new ListenerBuilder)->build();

$listener->onVerified(function (MessageVerifiedEvent $event) {
   $ipnMessage = $event->getMessage();
   
   // IPN message was verified, everything is ok! Do your processing logic here...
});

$listener->onInvalid(function (MessageInvalidEvent $event) {
   $ipnMessage = $event->getMessage();
   
   // IPN message was was invalid, something is not right! Do your logging here...
});

$listener->onVerificationFailure(function (MessageVerificationFailureEvent $event) {
    $error = $event->getError();
    
    // Something bad happend when trying to communicate with PayPal! Do your logging here...
});

$listener->listen();

Sandbox mode

When using one of the provided listener builders you can set your listener to use PayPal's sandbox for testing purposes:

$listenerBuilder = new ListenerBuilder();

$listenerBuilder->useSandbox(); // use PayPal sandbox

$listener = $listenerBuilder->build();

You can find some full usage examples in the examples directory.

Extending

To create your own service you must implement Mdb\PayPal\Ipn\Service.

To create your own message factory you must implement Mdb\PayPal\Ipn\MessageFactory.

To create your own listener builder it is best to extend Mdb\PayPal\Ipn\ListenerBuilder as this provides most of the boilerplate code needed to create a listener builder.

You will notice that when using any of the provided guzzle listener builders that there is a useSandbox method exposed. You can add this functionality to your listener builder by using the Mdb\PayPal\Ipn\ListenerBuilder\ModeDependentServiceEndpoint trait (see Mdb\PayPal\Ipn\ListenerBuilder\GuzzleListenerBuilder for usage example).

Notes

Testing

PayPal provides an IPN simulator here.