What hosting / server to use for a web application in several programming languages, with different databases (Windows / Linux)?

Question

PHP

Hello. The question is vague and big. I'm not sure that it is generally suitable for this resource, but I will try to describe it in a human way.
Overall goal: to build a complex of several applications, each of which does its own task, with a single user base.
Problem: one application is written in php (forum engine), uses mysql database. It is the users from this database that will be considered system users. Other applications are written in ASP.net MVC, they store their entities in mssql, they take users from mysql.
The question is something like this:
How to organize so that all services are spinning and available and can use each other's databases?
I understand that this area is large and complex, presumably. The sites themselves are individually either already working or in development. I looked towards Microsoft Azure, but there are a lot of things, it is not clear what to choose and how much it will cost.
The question is not only in hardware / hosting, I also do not have knowledge of how to logically place / distribute different databases.
I understand that the question is terrible, I do not even hope for a complete answer. At least for pieces of information where you can start.

Answer 1

I would put each task on a separate virtual machine inside one hypervisor, so it’s easier to maintain individual parts of the system without being afraid to screw everything up as a whole, it’s more convenient to backup and experiment. Communication of virtual machines would be organized through fake IP sharing access to each other. But this option is possible if the database is not very loaded. In any case, such a structure will allow you not to be afraid to fill up everything during experiments and the operation of one system will not affect the settings on others. OS choose what you like.