On the server:
- Web server: Apache 2 / nginx / IIS
- Database: MySQL 5.x (better 5.6 and up)
- PHP and some PHP extensions (check the requirements link below for an up to date information on this)
- The Ioncube PHP Loader
On the client: a recent version of Google Chrome, Mozilla Firefox, Microsoft Internet Explorer, Apple Safari, Opera.
Please check the link below for an extended explanation of the requirements.