public function bind($bindUser = null, $bindPass = null)
    {
        if (false === ldap_bind($this->ldapResource, $bindUser, $bindPass)) {
            throw new LdapClientException(
                sprintf(
                    'LDAP error: (%d) %s',
                    ldap_errno($this->ldapResource),
                    ldap_error($this->ldapResource)
                )
            );
        }
    }