Apache Rewrite Rules

Apache Re-write Rules

What?
Powerful mechanism
Hiding Actual URLs
Redirecting
Reformatting request URLs

Why?
Search engine friendly URLs
User Friendly URLs
Easy to remember
Hide underlying technology
index.php, index.axp, index.pl
Hide actual path of files

What we need?
Apache compiled with mod_rewrite module
mod_rewrite module should be enabled
RewriteEngine on

What does mod_rewrite do?
It catches URLs that meet specific
conditions, and rewrites them as it was
told to do.

But how does it do that?
Example:
RewriteRule ^/shortcut$ /complicated/url/here
<IfModule mod_rewrite.c> RewriteEngine on RewriteRule ^/shortcut$ /complicated/url/here
</IfModule>

The Structure of RewriteRule
RewriteRule Pattern Substitution [OptionalFlags]

What are OptionalFlags?
Not mandatory
Surrounded in square brackets
Comma separated
Commonly used flags:
F - Forbidden. The user will receive a 403 error.
L - Last Rule. No more rules will be proccessed if this one was successful.
R[=code] – Redirect.
NC – No Case

More condition using RewriteCond
RewriteCond directive defines a rule condition
Preserve RewriteRule with one or more RewriteCond directives
RewriteEngine On
RewriteCond %{HTTP_REFERER} !^$ [NC]
RewriteCond %{HTTP_REFERER} !^http://domain.com [NC]
RewriteCond %{HTTP_REFERER} !^http://www.domain.com [NC]
RewriteCond %{HTTP_REFERER} !^http://xxx.yyy.zzz.100 [NC]
RewriteRule ^.*$ http://www.domain.com/ [R,L]

Control Flow

Server Variables
%{ NAME_OF_VARIABLE }
HTTP_USER_AGENT
HTTP_REFERER,
HTTP_HOST
REQUEST_METHOD
REMOTE_HOST
QUERY_STRING
HTTPS
SERVER_PORT
etc...

Some Examples:
RewriteRule ^products/([0-9][0-9])/$ /product.php?prodID=$1
RewriteCond %{HTTP_HOST} !^www.example.com$ [NC]
RewriteRule .? http://www.example.com%{REQUEST_URI} [R=301,L]
RewriteRule ^/blog/?(.*)$ http://blog.domain.com/$1 [P,NC,L]
RewriteCond %{TIME_HOUR}%{TIME_MIN} >0700
RewriteCond %{TIME_HOUR}%{TIME_MIN} <1900
RewriteRule ^foo.html$ foo.day.html
RewriteRule ^foo.html$ foo.night.html

Thanks
:-)
http://webonrails.com

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Apache Rewrite Rules

by Akhil Bansal on Nov 28, 2008

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