I got an Invoicing system developed in 2005. The developer developed the system on Windows Platform using apache (XAMPP)/ smarty 2/php 5/ mysql (now upgraded to MariaDB).
I now have a requirement to upgrade the system to the latest version of smarty 3 or 4 (or some other framework)/ php. I also want to create new PHP applications.
I need some consulting advise on how to go about doing this.