... Apache uses environment variables in many ways to control operations and to communicate with other programs like CGI scripts. ... mod_setenvif . ... Related Directives . BrowserMatch . ... SetEnvIf . ... The most basic way to set an environment variable in Apache is using the unconditional SetEnv directive. ... For additional flexibility, the directives provided by mod_setenvif allow environment variables to be set on a per-request basis, conditional on characteristics of particular requests. ...