Facebook and Paypal have partnered to give friends a new way to split the bill, you fan access the feature the same way you pay with a card by tappoing the blue icons and then the green payment button.
In 2015 Messenger made is easier for friends to pay for dinner when it introduced the option to transfer money in-app with debit or credit card.
If you’d previously set up the feature to pay using your card, then you can change and choose PayPal to connect your account with Messenger. This feature is currenrly working on iOS and soon it will be available for Android. The sad part is that its only available to US users, everyone else will have to find other ways to spend their PayPal balance.