How to avoid php flooding?

suppose i have a file on my server "action.php"

and i have displayed HTML form for users to enter their details.

So i will make html form as

so now the above code is easily visible when we see the page source, and any one can make VB application and flood the action.php with input details..

Is there any way to hide action.php, i-e the user could not see the action.php file path ??

The method of CAPTCHA is secured to avoid flooding but it can be used in my form page only, if the user can make the form on his own and post the data to action.php or he can also make a VB application to post data to action.php .

Any idea ?

Why would anyone bother to flood your server with requests? And why bother with action.php specifically? Why not index.php or any of dozens of php files on your server? Does action.php send out emails that it should be targetted?

Action.php was an example ..

Thanks for the reply..

Issue is resolved > using google Recaptcha