How to sync or update data in to Dynamics 365 Sales Account, Contact, Quotes, Opportunities, Invoice and Payment information from the legacy PHP based application with my sql database.
There's no easy answer to this one - there are myriad ways you can achieve a near real-time integration. Dataverse has the web API and the organisation service, there are Power Platform connectors; the recommendation for the way you connect and the technology you utilize will be based on factors such as data volumes, business criticality, licensing/cost requirements... I recommend you make a post here https://community.dynamics.com/365/sales/f/dynamics-365-for-sales-forum with some further details about the requirements of your integration and the function of your legacy system.
