Name

SetEnvIf and SetEnvIfNoCase

Synopsis

SetEnvIf attribute regex envar[=value] [..] 
SetEnvIfNoCase attribute regex envar[=value] [..] 
Server config, virtual host, directory, .htaccess (from v 1.3.14)

The attribute can be one of the HTTP request header fields, such as Host, User-Agent, Referer, and/or one of the following:

Remote_Host

The client’s hostname, if available

Remote_Addr

The client’s IP address

Remote_User

The client’s authenticated username, if available

Request_Method

GET, POST, etc.

Request_URI

The part of the URL following the scheme and host

The NoCase version works the same except that regular-expression matching is evaluated without regard to letter case.