Filter url

[mmarif4u]

I want to filter some urls on my site.

for example:

http://localhost/CMS/db.php?rand=3af7e4c440a43bde0a308839218a2b63e28d81aa&action=t

The above url has 82 characters long.

If for example some one add something to it:

http://localhost/CMS/db.php?rand=3af7e4c440a43bde0a308839218a2b63e28d81aa&action=t&do=select * from table

This is just example.

So how can i filter that url to just allow rand and action,which i already filter.but adding new GET is possible to write there.

I know about strlen and filter_var.but i dont think that will solve this problem.

 

Any ideas...

Arif