使用地址栏内容重定向html页面

I'm looking to achieve similar functionality on my site as facebook does for its pages section. Basically I want users to be able to navigate to:

www.mysite.com/school123

Then behind the scenes I would be able to locate 'school123' using URL with PHP, then I can find the correct path in the database and redirect to the correct path (example: www.mysite.com/pages/schools/school123/index.php ). Problem is as the page doesn't exist I get a 404 error.

My question is should I look at modifying the 404 page to do the DB lookup & redirect my page or is there a better way of doing this?

Thank you in advance

Modifying the 404 page is one way to do it, then obviously overwriting the 404 Header using PHP. But this isn't the most practical of ways, I am making the assumption of Apache; as Claudio Bredfeldt said: http://httpd.apache.org/docs/current/mod/mod_rewrite.html and then after your DB Lookup for the Pointer/Reference to the file/data you should use http://www.php.net/manual/en/function.readfile.php to quickly return it on the initial URL without a redirect. This will lower overhead.

1> you can pass school and 123 as parameter to your url as somepage.php?t=shool&n=123, and depending on parameter you can redirect.

2>in your root folder you can make folder as school123 and in that you can have index.php file which will redirect to www.mysite.com/pages/schools/school123/index.php