Code to Prevent Form repetition based on Name & DOB

I'm a joomla Developer, want a PHP code to avoid user from filling the form more than once. i.e., as he/she enters开发者_如何学Python the name & DOB, if there is already a record in DB of same name & DOB an automatic message should be generated preventing the user from filling the form twice

If you mean that the user is not logged in, then starts entering the form data, then the only way to accomplish what you want is to use AJAX to validate the name and DOB as soon as they are entered. There is a registration extension that has AJAX validation that you could probably modify to suit your needs.

http://extensions.joomla.org/extensions/access-a-security/authentication/7361