Mysql with URL keyword

Hello.

I have a "home made" php-mysql website available through http://mydomain.com.

I want to achieve the following:

Let`s say I enter the url : http://mydomain.com/something 
I would like to read this url, get the part of a url called "something" and lookup this word("something") in mysql database.

I`ve created a new folder called "something" containing index.php which reads url, gets the part of url "something" and querys a select.

But this is not a good solution when there are a lot of words in a database. Does anyone have a solution how to achieve the same, without having to create a directory for each word in database?

thx