<div class="directive-section"><h2><a name="Header" id="Header">Header</a> <a name="header" id="header">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure HTTP response headers</td></tr>
-<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Header [<var>condition</var>] add|append|echo|edit|edit*|merge|set|unset|note
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Header [<var>condition</var>] add|append|echo|edit|edit*|merge|set|setifempty|unset|note
<var>header</var> [<var>value</var>] [<var>replacement</var>]
[early|env=[!]<var>variable</var>]|expr=<var>expression</var>]
</code></td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_headers</td></tr>
-<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Default condition was temporarily changed to "always" in 2.3.9 and 2.3.10</td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Default condition was temporarily changed to "always" in 2.3.9 and 2.3.10. SetIfEmpty available since 2.4.7.</td></tr>
</table>
<p>This directive can replace, merge or remove HTTP response
headers. The header is modified just after the content handler
<dt><code>setifempty</code></dt>
<dd>The request header is set, but only if there is no previous header
- with this name</dd>
+ with this name. Available in 2.4.7 and later.</dd>
<dt><code>unset</code></dt>
<dd>The response header of this name is removed, if it exists.
<div class="directive-section"><h2><a name="RequestHeader" id="RequestHeader">RequestHeader</a> <a name="requestheader" id="requestheader">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure HTTP request headers</td></tr>
-<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RequestHeader add|append|edit|edit*|merge|set|unset
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RequestHeader add|append|edit|edit*|merge|set|setifempty|unset
<var>header</var> [<var>value</var>] [<var>replacement</var>]
[early|env=[!]<var>variable</var>]|expr=<var>expression</var>]
</code></td></tr>
<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_headers</td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>SetIfEmpty available in 2.4.7 and later</td></tr>
</table>
<p>This directive can replace, merge, change or remove HTTP request
headers. The header is modified just before the content handler
<dt><code>setifempty</code></dt>
<dd>The request header is set, but only if there is no previous header
- with this name</dd>
+ with this name. Available in 2.4.7 and later.</dd>
<dt><code>unset</code></dt>
<dd>The request header of this name is removed, if it exists. If
will exit.</td></tr>
<tr class="odd"><td><a href="mod_unixd.html#group">Group <var>unix-group</var></a></td><td> #-1 </td><td>s</td><td>B</td></tr><tr class="odd"><td class="descr" colspan="4">Group under which the server will answer
requests</td></tr>
-<tr><td><a href="mod_headers.html#header" id="H" name="H">Header [<var>condition</var>] add|append|echo|edit|edit*|merge|set|unset|note
+<tr><td><a href="mod_headers.html#header" id="H" name="H">Header [<var>condition</var>] add|append|echo|edit|edit*|merge|set|setifempty|unset|note
<var>header</var> [<var>value</var>] [<var>replacement</var>]
[early|env=[!]<var>variable</var>]|expr=<var>expression</var>]
</a></td><td></td><td>svdh</td><td>E</td></tr><tr><td class="descr" colspan="4">Configure HTTP response headers</td></tr>
<tr><td><a href="mod_mime.html#removetype">RemoveType <var>extension</var> [<var>extension</var>]
...</a></td><td></td><td>vdh</td><td>B</td></tr><tr><td class="descr" colspan="4">Removes any content type associations for a set of file
extensions</td></tr>
-<tr class="odd"><td><a href="mod_headers.html#requestheader">RequestHeader add|append|edit|edit*|merge|set|unset
+<tr class="odd"><td><a href="mod_headers.html#requestheader">RequestHeader add|append|edit|edit*|merge|set|setifempty|unset
<var>header</var> [<var>value</var>] [<var>replacement</var>]
[early|env=[!]<var>variable</var>]|expr=<var>expression</var>]
</a></td><td></td><td>svdh</td><td>E</td></tr><tr class="odd"><td class="descr" colspan="4">Configure HTTP request headers</td></tr>