Build a web app and migrate data from Sharepoint to new app possible using PHP

We currently use Sharepoint to manage customers projects. Every customer can login and have a personalised dashboard which pulls data from excel spreadsheets to generate the customer dashboard, there are also links to a central library of PDF's that the customer can pull up from the dashboard for reference. There should be an admin site for creating new client pages and obviously a client login side. Happy to discuss in more details to explain what we need. We would provide the server for hosting the app.