document new RequestHeader behaviour

PR: 27951
Submitted by: vincent gryzor.com (Vincent Deffontaines)

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@103270 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/docs/manual/mod/mod_headers.xml b/docs/manual/mod/mod_headers.xml
index 7e10eb4ed23fb66ab34767e22b273cf8b21eb98f..c816f19f957d095aa218b04d78326a212afff3fb 100644 (file)
--- a/docs/manual/mod/mod_headers.xml
+++ b/docs/manual/mod/mod_headers.xml
@@ -128,7 +128,7 @@ is available only in Apache 2.0</compatibility>
 <name>RequestHeader</name>
 <description>Configure HTTP request headers</description>
 <syntax>RequestHeader set|append|add|unset <var>header</var>
-[<var>value</var>]</syntax>
+[<var>value</var> [env=[!]<var>variable</var>]]</syntax>
 <contextlist><context>server config</context><context>virtual host</context>
 <context>directory</context><context>.htaccess</context></contextlist>
 <override>FileInfo</override>
@@ -171,6 +171,16 @@ is available only in Apache 2.0</compatibility>
     <var>value</var> contains spaces, it should be surrounded by double
     quotes. For unset, no <var>value</var> should be given.</p>
 
+    <p>When the <directive>RequestHeader</directive> directive is used with the
+    <code>add</code>, <code>append</code>, or <code>set</code> argument, a
+    fourth argument may be used to specify conditions under which the action
+    will be taken. If the <a href="../env.html">environment variable</a>
+    specified in the <code>env=...</code> argument exists (or if the environment
+    variable does not exist and <code>env=!...</code> is specified) then the
+    action specified by the <directive>RequestHeader</directive> directive will
+    take effect. Otherwise, the directive will have no effect on the
+    request.</p>
+
     <p>The <directive>RequestHeader</directive> directive is processed
     just before the request is run by its handler in the fixup phase.
     This should allow headers generated by the browser, or by Apache