.htaccess: Hide URL variables
===

I have no idea how to play with .htaccess file to change / hide variables from URL

I have url

    http://localhost/my_site/project-detail/?pro_id=7
and I want to either hide **pro_id=7** like

    http://localhost/my_site/project-detail/
but could be able to catch this $_GET['pro_id'] in my php script file.

or 

    http://localhost/my_site/project-detail/7