<li><img alt="" src="../images/down.gif" /> <a href="#alias">URL Aliasing</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#vhosts">Virtual Hosting</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxy">Simple Proxying</a></li>
-<li><img alt="" src="../images/down.gif" /> <a href="#setenv">Environment Variable Testing</a></li>
</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module documentation</a></li><li><a href="intro.html">mod_rewrite introduction</a></li><li><a href="remapping.html">Redirection and remapping</a></li><li><a href="access.html">Controlling access</a></li><li><a href="vhosts.html">Virtual hosts</a></li><li><a href="proxy.html">Proxying</a></li><li><a href="rewritemap.html">Using RewriteMap</a></li><li><a href="advanced.html">Advanced techniques and tricks</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<code>ProxyPass</code>, and so may preempt what you're trying to
accomplish.</p>
-</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
-<div class="section">
-<h2><a name="setenv" id="setenv">Environment Variable Testing</a></h2>
-
-<p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is frequently used to take a particular
-action based on the presence or absense of a particular environment
-variable or request header. This can be done more efficiently using the
-<code class="directive"><a href="../mod/core.html#if"><If></a></code>.</p>
-
-<p>Consider, for example, the common scenario where
-<code class="directive">RewriteRule</code> is used to enforce a canonical
-hostname, such as <code>www.example.com</code> instead of
-<code>example.com</code>. This can be done using the <code class="directive"><a href="../mod/core.html#if"><If></a></code> direct, as shown here:</p>
-
-<div class="example"><p><code>
-<If "$req{Host} = 'example.com'"><br />
-RedirectMatch (.*) http://www.example.com$1
-</If>
-</code></p></div>
-
-<p>This technique can be used to take actions based on any request
-header, response header, or environment variable, replacing
-<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> in many common scenarios.</p>
-
-<p>See especially the <a href="../expr.html">expression evaluation
-documentation</a> for a overview of what types of expressions you can
-use in <If> sections, and in certain other directives.</p>
-
</div></div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>