Adldap\Models\Group::addMember PHP Method

    public function addMember($entry)
    {
        $entry = $entry instanceof Model ? $entry->getDn() : $entry;
        if (is_null($entry)) {
            throw new InvalidArgumentException('Cannot add member to group. The members distinguished name cannot be null.');
        }
        $this->addModification(new BatchModification($this->schema->member(), LDAP_MODIFY_BATCH_ADD, [$entry]));
        return $this->save();
    }