Hosting an internal php web application on a public web server

How do i host an internal php web application on a public web server .

i need to host a private web site on the web. I can create a login but have some concerns.

If someone knows a link after the login , how can i stop him to go to that link?

eg

my web site www.myapp.com

this will ask for a login

when the login happens , he goes to http://ift.tt/28Q5WWI

How can i stop some one typing http://ift.tt/28Q5WWI and bypassing the login?

Regards

Azhar