1.1. Requirements
HelpSpot requires PHP 4.3.10+, including PHP 5. HelpSpot should run on any operating system supported by PHP and has been tested on various types of Linux, FreeBSD, Mac OSX, and Windows 2003 Server as an ISAPI module.
Databases supported by HelpSpot include MySQL 4.1.2+, MySQL 5.x, PostgreSQL 8, Microsoft SQL Server 2000, Microsoft SQL Server 2005 and Microsoft SQL Server 2008. Each database has it's own strengths and weaknesses, which you should weigh when deciding which one to choose. All are high quality production level database systems.
The primary difference in regards to HelpSpot are that MySQL supports full text indexing which allows for superior searching but does not support transactions. This has not been a factor during our testing, however, if you plan on running HelpSpot on a heavily loaded or unstable server then this may be something to consider. PostgreSQL does support transactions, but not full text indexing so the searching is a bit more limited. Microsoft SQL Server supports both transactions and full text indexing.
Finally, HelpSpot requires the Zend Optimizer to be installed, version 3 or higher. If you're on a hosted server it should already be installed for you. If you're running your own server the installation page has links to the optimizer downloads for each platform.