The control of internal environment variables that are used by various Apache HTTP Server modules are controlled by the module mod_env.
By default module 'mod_env' will not be enabled in apache2.4. This will cause below error while using 'SetEnv' in htacess file.
Invalid command 'SetEnv', perhaps misspelled or defined by a module not included in the server configuration
To resolve this problem, we need to install the module 'mod_env' manually.
For easyapache4 users,
#yum install ea-apache24-mod_env.x86_64