PHP Point of Sale -- Modernize billing by using PayPal pro pay flow integration

Currently for our web site we offer 3 types of products available for purchase: 1. Digital delivery of software product 2. Cloud/subscription product (paid monthly or yearly with 14 day trial) 3. Various hardware such as credit card processing machines and related devices For these products we have been using PayPal buttons where the transactions take place offsite on PayPal's website. We are looking to move all billing into our web site using PayPal payments pro pay flow edition and make it easier to manage. We still need to support the old billing model for cloud/subscription customers; but all new customers should use the new billing system. This allows for a better experience as all transactions take place in our site. The detailed requirements are attached to this job posting. Developer requirements: - Developer should be experienced with PayPal payments pro pay flow edition and PayPal billing in general - Strong knowledge of PHP and ability to quickly understand existing code base - Timely completing of project - Detailed oriented and ability to suggest ideas if specifications are not clear or can be impoverished. - Must be able to use git and github very well - Must be available during USA business hours