Apache/PHP and Digital Certificates
 

I want to configure the following in Apache/PHP

A user comes to a url and has to present a digital certificate in order to access it. Apache will check the certificate and CN and only allow access once it ahs been authenticated.

I then need details of the CN passed to a PHP script.

Is this possible ? I understand the SSL Directives required for apache, but am not sure how to pass the CN to PHP

TIA
Dave