Aaron D. Campbell

This plugins gives you a great framework to use for integrating with PayPal. 
It stores both live and sandbox API credentials and allows you to switch back 
and forth easily. All NVP API calls are passed through the framework and 
default values such as API version, API credentials, and even currency code are 
added to the request based on settings from the admin panel.
It also has a built in IPN listener that validates messages as coming from 
PayPal then throws WordPress actions based on messages received. For example it 
throws “paypal-recurring_payment_profile_cancel” when someone cancels a 
recurring payment that they had set up with you. It passes along all the info 
that PayPal sent to the action, so it’s simple to create other plugins that use 
this one.
Requires PHP5.
You may also be interested in WordPress tips and tricks at <a href="http://wpinformer.com" rel="nofollow ugc">WordPress Informer</a> or gerneral <a href="http://webdevnews.net" rel="nofollow ugc">Web Developer News</a>

PayPal Framework

PayPal integration framework and admin interface as well as IPN listener.

Automattic

WooCommerce

Remi Corson

royho

Akeda Bagus

Allen Snook

danieldudzic

SkyVerge

Praveen a11n

Phil

Thomas Shellberg

Hannah S.L.

AW a11n

Mike M. a11n

Zandy Ring

D Smith a11n

Steve E.a11n

Accept credit cards, Apple Pay, Google Pay, PayPal, Venmo, ACH Direct Debit, BNPL, local payment methods, and more with PayPal Enterprise Payments (formerly Braintree) for WooCommerce — with Fastlane accelerated checkout built in. Customers can save their card details or link a PayPal account for an even faster checkout experience.
<h4>Features</h4>
<ul>
<li>No redirects — keep customers on your site for payment, reducing the risk of abandoned carts.</li>
<li>Security first; PCI compliant, with 3D Secure verification and Strong Customer Authentication (SCA).</li>
<li>Express checkout options, including Buy Now and PayPal Checkout buttons. Customers can save their card details, link a PayPal account, or pay with Apple Pay.</li>
<li>Optimized order management; process refunds, void transactions, and capture charges from your WooCommerce dashboard.</li>
<li>Route payments in certain currencies to different Braintree accounts (requires currency switcher).</li>
<li>Compatible with WooCommerce Subscriptions and WooCommerce Pre-Orders.</li>
</ul>
<h4>Safe and secure — every time</h4>
Braintree’s secure Hosted Fields provide a seamless way for customers to enter payment info on your site without redirecting them to PayPal.
It’s <a href="https://listings.pcisecuritystandards.org/documents/Understanding_SAQs_PCI_DSS_v3.pdf" rel="nofollow ugc">PCI compliant</a> and supports SCA and 3D Secure verification, so you always meet security requirements — without sacrificing flexibility. Plus, Braintree’s <a href="https://articles.braintreepayments.com/guides/fraud-tools/overview" rel="nofollow ugc">fraud tools</a> protect your business by helping detect and prevent fraud.
<h4>Even faster checkouts</h4>
Customers can save their credit and debit card details or link a PayPal account to fast-forward checkout the next time they shop with you. Adding PayPal Checkout and Buy Now buttons to your product, cart, and checkout pages makes purchasing simpler and quicker, too.
<h4>Get paid upfront and earn recurring revenue</h4>
Take charge of how you sell online. PayPal Enterprise Payments (formerly Braintree) supports <a href="https://woocommerce.com/products/woocommerce-subscriptions/" rel="nofollow ugc">WooCommerce Subscriptions</a> — the perfect solution for earning recurring revenue. It’s also compatible with <a href="https://woocommerce.com/products/woocommerce-pre-orders/" rel="nofollow ugc">WooCommerce Pre-Orders</a>, enabling you to accept payment upfront or as products ship.

PayPal Enterprise Payments (formerly Braintree) for WooCommerce

The official PayPal Enterprise Payments extension for WooCommerce. Accept credit cards, PayPal, Apple Pay, Google Pay, Venmo, ACH Direct Debit, BNPL,  …

PayPal Framework vs PayPal Enterprise Payments (formerly Braintree) for WooCommerce