Apache is a free and open-source cross-platform web server software.
CentOS is a Linux distribution that provides a free, community-supported computing platform functionally compatible with its upstream source, Red Hat Enterprise Linux (RHEL).
PHP is a general-purpose scripting language used for web development.
SimpleSAMLphp is an open-source PHP authentication application that provides support for SAML 2.0 as a Service Provider (SP) or Identity Provider (IdP).