Clean URLs with Apache - Page 2
       by Miran Lipovaca aka foodpk | 7 April 2007

In the previous page, you learned about the advantages of clean URLs, and we just got started explaining what the code you copied and pasted was. In this page, let's continue by learning about rewrite rules.

OK, so now comes the rewrite rule. A rewrite rule is comprised of a regular
expression (the request is matched against it) and if it matches, it gives the
client the file specified afterwards. Now I can't go about explaining regular
expressions as a whole, for that's a pretty hefty subject, but we'll take a glance at
what's done here.

If we take a look at the first rewrite rule:

RewriteRule ^([a-zA-Z0-9\-]+)/?$  /index.php?category=$1 [L,QSA]

it tells the server to match any character from a-z, A-Z, 0-9 and the dash - character. The + means it matches either 1 or many of those characters. Then there's a dash / and a question mark. A question mark after the dash means 'match either one or no dash at all'. The $ means the end of the line.

So the first regular expression basically says: "If something that's comprised of letters, numbers and the dash line, catch it. It doesn't matter if it has a slash afterwards or not."

Whatever we put in the parenthesis, we can use as a variable. After the regular
expression, we reach that variable by using $1, or $2 if it's the second variable,
and so on.

As you can now probably see, the first rewrite rule turns, say, http://yoursite.com/index.php ?category=cooking into http://yoursite.com/cooking (or http://yoursite.com/cooking/) Pretty, sweet, huh?

The second and third rule do the same thing, except they come to effect when someone
requests two 'directories', like http://yoursite.com/cooking/pasta. Then it gives
that person http://yoursite.com/index.php?section=cooking&page=pasta

In the example I've included the ability to read three 'fake directories' (so you can do http://yoursite.com/one/two /three), but if you need more, just add another
rewrite rule, I'm sure you can see what the pattern used is.

Note

The QSA in the [L,QSA] means that you can append query strings to the URL. So http://yoursite.com/cooking/
pasta/4/?show=something
will work.


Clean URLs in Action
Below is a simple example of how to put all this mod rewriting to work. First put
the above .htaccess in the root folder. Then, use the following code as your index.php:

Let's say the user requests http://yoursite.com/aboutme. First the .htaccess will
interpret that and tell the server to call http://yoursite.com/index.php ?category=aboutme. Then the index.php will set $file to aboutme.php and check if it exists. If it exists, it will include aboutme.php into the page. If it doesn't, it will tell the user that tha page wasn't found.

The above was just a simple example, you can use what we learned here to get many
more variables (like http://yoursite.com/one/two /three) and then include them
however you want. Most of the time you will be including some of them while using
others to get stuff out of a database according to them.

One final note, if you have problems with links and images becoming broken after
using this, you should put a base tag in the head of your (X)HTML document, like so:

<base href="http://yoursite.com/" />

The base tag tells the browser where to begin looking when relative paths are in play.

If you have any questions regarding mod rewriting, feel free to ask them in the
forums!

High five!

miran lipovaca aka foodpk

 


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