Apache HTTP Server Version 2.3
Apache HTTP Server Version 2.3
Available Languages: en
This document supplements the mod_rewrite
reference documentation. It describes
perhaps one of the most important concepts about mod_rewrite - namely,
when to avoid using it.
mod_rewrite should be considered a last resort, when other alternatives are found wanting. Using it when there are simpler alternatives leads to configurations which are confusing, fragile, and hard to maintain. Understanding what other alternatives are available is a very important step towards mod_rewrite mastery.
Note that many of these examples won't work unchanged in your particular server configuration, so it's important that you understand them, rather than merely cutting and pasting the examples into your configuration.
mod_alias provides the Redirect and RedirectMatch directives, which provide a
means to redirect one URL to another. This kind of simple redirection of
one URL, or a class of URLs, to somewhere else, should be accomplished
using these directives rather than RewriteRule. RedirectMatch
allows you to include a regular expression in your redirection criteria,
providing many of the benefits of using RewriteRule.
A common use for RewriteRule is to redirect an entire
class of URLs. For example, all URLs in the /one directory
must be redirected to http://one.example.com/, or perhaps
all http requests must be redirected to
https.
These situations are better handled by the Redirect
directive. Remember that Redirect preserves path
information. That is to say, a redirect for a URL /one will
also redirect all URLs under that, such as /one/two.html
and /one/three/four.html.
To redirect URLs under /one to
http://one.example.com, do the following:
Redirect /one/ http://one.example.com/
To redirect http URLs to https, do the
following:
<VirtualHost *:80>
ServerName www.example.com
Redirect / https://www.example.com/
</VirtualHost >
<VirtualHost *:443>
ServerName www.example.com
# ... SSL configuration goes here
</VirtualHost >
The use of RewriteRule to perform this task may be
appropriate if there are other RewriteRule directives in
the same scope. This is because, when there are Redirect
and RewriteRule directives in the same scope, the
RewriteRule directives will run first, regardless of the
order of appearance in the configuration file.
In the case of the http-to-https redirection, the use of
RewriteRule would be appropriate if you don't have access
to the main server configuration file, and are obliged to perform this
task in a .htaccess file instead.
The Alias directive
provides mapping from a URI to a directory - usually a directory outside
of your DocumentRoot. Although it
is possible to perform this mapping with mod_rewrite,
Alias is the preferred method, for reasons of simplicity
and performance.
Alias /cats /var/www/virtualhosts/felines/htdocs
The use of mod_rewrite to perform this mapping may be
appropriate when you do not have access to the server configuration
files. Alias may only be used in server or virtualhost context, and not
in a .htaccess file.
Symbolic links would be another way to accomplish the same thing, if
you have Options FollowSymLinks enabled on your
server.
Although it is possible to handle virtual hosts
with mod_rewrite, it is seldom the right way. Creating individual
<VirtualHost> blocks is almost always the right way to go. In the
event that you have an enormous number of virtual hosts, consider using
mod_vhost_alias to create these hosts automatically.
Third-party modules such as mod_macro are also useful for creating a large number of virtual hosts dynamically.
Using mod_rewrite for vitualhost creation may be
appropriate if you are using a hosting service that does not provide
you access to the server configuration files, and you are therefore
restricted to configuration using .htaccess files.
See the virtual hosts with mod_rewrite document for more details on how you might accomplish this if it still seems like the right approach.
RewriteRule provides the [P] flag to pass rewritten URIs through
mod_proxy. As with any use of mod_rewrite,
you want to ask yourself whether it's really the best solution.
Using SetEnvIf and <If> (2.3 and later.)
Available Languages: en
