The <If> directive evaluates an expression at runtime, and applies the enclosed directives if and only if the expression evaluates to true. For example:

<If "-z req('Host')">

would match HTTP/1.0 requests without a Host: header. Expressions may contain various shell-like operators for string comparison ( == , != , < , ...), integer comparison ( -eq , -ne , ...), and others ( -n , -z , -f , ...). It is also possible to use regular expressions,

<If "%{QUERY_STRING} =~ /(delete|commit)=.*?elem/">

shell-like pattern matches and many other operations. These operations can be done on request headers ( req ), environment variables ( env ), and a large number of other properties. The full documentation is available in Expressions in Apache HTTP Server.

Only directives that support the directory context can be used within this configuration section.

See also

• Expressions in Apache HTTP Server, for a complete reference and more examples.
• <ElseIf>
• <Else>
• How <Directory>, <Location>, <Files> sections work for an explanation of how these different sections are combined when a request is received. <If> , <ElseIf> , and <Else> are applied last.