We have an ecommerce website where the customer enters their nank details, name and credit card. These details are emailed to us by means of a PHP Form Mailer. No details are retained in our website MySQL database. The customers name and bank details must be displayed on screen after customer has left the order page. These details are currently being carried in a PHP session. For security reasons, I would like these details to be cleared once a customer has either clicked a button, or been inactive for more than a few minutes. Nothing should be cached on the PC or visible if the page is clicked back to or revisted by clicking in history. Various web based email companies have this feature - you can't read the email of someone who has logged out or been inactive for a few minutes. It's not cached on the hard drive.
Providers who specialise in website security and have their own websites would be preferred for this project, as will providers who are physically based in the UK. I have marked this as a $30-$100 budget project but will consider whatever quotations are appropriate.