Establishing a TLS connection to LDAP server

Hi, I've read a great article about connecting securely to LDAP using PHP (http://www.novell.com/coolsolutions/trench/5838.html). It works nice :-) I would like now to authenticate the both sides when establishing the TLS tunnel. In other words, my OpenLDAP requires a client certificate. After searching many hours and trying different solutions (ldap.conf, environment variables...), I still have the same problem : the client certificate isn't sent by my apache server :-(( Do you have any idea in order to solve it ? Thanks in advance, Best Regards, Aurelien