count restricted Form

How to restrict signup form to a specific number of times

[seo24x7]

I am trying to build a form wherein users can sign up for training classes. Each class can have only 10 members. Once 10 students have signed up, the form should display a message saying "Fully booked". How do I restrict the form to only 10 signups? I am using PHP and MySQL

[jatar_k]

is each form restricted to one class?
or is there a drop down or something to select which class?
how do you store the signups?