im currently writing a PHP system to do project and order management for a large number of companies,
I have a few requirements and not 100% sure best options any help on any of the below would be greatly received
1) Heartbeat between multiple servers of the mysql database
2) Information can be entered at any server at any datacenter and the other servers will get the information relayed incase access to 1 data center goes down.
3) The system will have be kept upto date as it relates to Goverment proceedure which updates, do i make a multi user / company system from 1 database or do i do an installation for each of the 900 companies, if so how do i get updates of the PHP and SQL tables to the companies,