The PayPal SDK can be found here:
[login to view URL]
App will be based on the Paypal Retail SDK.
App will accept information from a PHP based Point of Sale System.
App Needs to Process Payment Information and send Response Codes to the Point of Sale.
The App also need to gather Signature and send it to the POS.
Webhooks will need to be added to the PHP based Point of Sale System.