Hello I\'m trying to use my ldap test server in order to authenticate users in openca.
I\'m currently connecting through phpldapadmin with :
Login
The base dn is dc=example,dc=com. 
I don't know about openca, but I will try this answer since you got very little traffic so far.
A base dn is the point from where a server will search for users. So I would try to simply use admin as a login name. 
If openca behaves like most ldap aware applications, this is what is going to happen :
admin will be done by the server starting at the base dn (dc=example,dc=com).cn=admin,dc=example,dc=com) will be used to bind with the supplied password.Getting step 1 right is the hardest part, but mostly because we don't get to do it often. Things you have to look out for in your configuraiton file are :
dn your application will use to bind to the ldap server. This happens at application startup, before any user comes to authenticate. You will have to supply a full dn, maybe something like cn=admin,dc=example,dc=com.objectClass for your admin user. It will be either inetOrgPerson or user. There will be others like top, you can ignore them. In your openca configuration, there should be a string like (objectClass=inetOrgPerson). Whatever it is, make sure it matches your admin user's object Class. You can specify two object class with this search filter (|(objectClass=inetOrgPerson)(objectClass=user)). Download an LDAP Browser, such as Apache's Directory Studio. Connect using your application's credentials, so you will see what your application sees.
Either you set LDAP_DOMAIN variable or you misconfigured it. Jump inside of ldap machine/container and run:
slapcat > backup.ldif
If it fails, check punctuation, quotes etc while you assigned variable "LDAP_DOMAIN" Otherwise you will find answer inside on backup.ldif file.