How to read certificate values of HTTPS webserver

Hi, I have a SSL enabledd webserver which is CA self signed. So when client hits the server , the server shows the client his certificate and as its self signed so the client browser add the exception and proceed. Now when the client hit the webserver and server showed its certificate; is there any way I can get the informations from that certificate because I have no idea how to let php know when the server sent its certificate so that it can fetch the information and how to read? Because I am trying of doing the authentication based on the certificate like take the cn value from certificate and match with a database and if match found the client can proceed. Thank you.