Well, using ldap_search on a known variable provides an array of information...
$conn = ldap_connect("ldap.server");
ldap_bind($conn, "Username", "Password");
ldap_set_option($conn, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($conn, LDAP_OPT_REFERRALS, 0);
$username = "blah blah";
$string = "ou=domain,dc=company,dc=com","(cn=".$username.")";
$search = ldap_search($conn, $string);
$info = ldap_get_entries($conn, $search);
print_r($info);
That string (base dn) will be different for you, but should give you an idea.