Mod_rewrite and MySql - mod-rewrite

Question

I have a url eg. www.example.com/user.php?user_id=9 , where the user_id field maps to one of the pk in the user table . I don't want the url to be like this , instead i want to have a url like www.example.com/user/Aditya-Shukla.i am using apache 2 and I understand that mod-rewrite module has sets of rewriting rules which can be used to create url alias.
My question is
I have all href in the form www.example.com/user.php?user_id=9. So to change the url I suppose i have to change all the href's to the www.example.com/user/Aditya-Shukla and for rewriting the rule do a query to get a record?
Is there a better solution .

Answer 1

No, mod_rewrite does not have sets of rewriting rules. It rather provides directives to build rules based on regular expression patterns that can be combined with additional conditions.
In your case you would build a rule that takes any requested URL path that starts with /user/ and has another path segment following and rewrites it internally to your user.php, like:
RewriteEngine on
RewriteRule ^/user/([^/]+)$ /user.php?name=$1
The first directive RewriteEngine on is just to enable mod_rewrite. And the second directive RewriteRule … is the rule as described above: ^/user/([^/]+)$ is the pattern that matches any URL path that starts with /user/ (i.e. ^/user/) and that is followed by one path segment (i.e. ([^/]+)$). That request is then rewritten internally to /user.php while the matched path segment behind the /user/ is used as a parameter value for the name parameter ($1 is a reference to the matched value of the first group denoted with (…)).
So this will rewrite a request of /user/Aditya-Shukla internally to /user.php?name=Aditya-Shukla. You can then use that user name and look it up in your table.

Answer 2

You can either add a RewriteRule that will rewrite user/Aditya-Shukla to user.php?user_name=Aditya-Shukla and handle the rest in your code.
RewriteEngine On
RewriteRule ^user/(.*)$ user.php?user_name=$1
Or using a RewriteMap directive to lookup usernames, which will allow to rewrite user/Aditya-Shukla directly to user.php?user_id=9

Answer 3

I presume that within your own site you will always create the canonical form of the URL, i.e.:
/user/Aditya-Shukla
...and you are just having to deal with outside links that are not in canonical form, i.e. "old links" like:
www.example.com/user.php?user_id=9
mod_rewrite may not be suitable for remapping in this situation. I am presuming you may have very many users, and that number may grow. mod_rewrite does have a RewriteMap directive and yes there are ways to generate your map dynamically, but I don't think that would be a good design (to dynamically create a map of userId-to-userName dynamically every time your rewrite rule matches...)
Instead you should simply write your user.php code to lookup the correct userName, assemble the canonical form of URL you want, and send a redirect back to the client. Something like:
Header( "HTTP/1.1 301 Moved Permanently" );
Header( "Location: http://www.example.com/user/Aditya-Shukla" );
You should probably also use a 301 redirect (instead of 302) to indicate this is a "permanent" URL change, which will help search bots index your site correctly if it encounters an "old style" URL out there.
-broc