Postprocess saved data

Hi all,
​
I have a form including a "Save data" and insert a record. Afterwards I would like to postprocess the data using JDatabase. The problem is to get the "aid" of the newly inserted record. The debugger shows:

Array
(
    [submit_validate_fields] => Array
        (
            [log] => Automatic validation enabled.
            [var] => 1
        )

    [save_data3] => Array
        (
            [data] => Array
                (
                    [created] => 2019-05-08 06:26:57
                    [user_id] => 54
                    [company] => Katholische Panzerwaschanstalt GmbH
                    [address] => Musterstrasse 4
                    [country] => DEU
                    [product] => tce
                    [expiration] => 2019-05-31 08:26:00
                    [state] => 0
                    [operating_system] => ["unx"]
                    [databases_mainframe] => ["db2"]
                    [databases_server] => ["my"]
                    [next_message] => My message
                )

            [_success] => Data saved successfully
            [log] => Array
                (
                    [0] => INSERT INTO `jos_chronoforms_data_reservierungseintrag` (`created`, `user_id`, `company`, `address`, `country`, `product`, `expiration`, `state`, `operating_system`, `databases_mainframe`, `databases_server`, `next_message`)  values  ('2019-05-08 06:26:57', '54', 'Katholische Panzerwaschanstalt GmbH', 'Musterstrasse 4', 'DEU', 'tce', '2019-05-31 08:26:00', '0', '["unx"]', '["db2"]', '["my"]', 'My message');
                )

            [var] => Array
                (
                    [created] => 2019-05-08 06:26:57
                    [user_id] => 54
                    [company] => Katholische Panzerwaschanstalt GmbH
                    [address] => Musterstrasse 4
                    [country] => DEU
                    [product] => tce
                    [expiration] => 2019-05-31 08:26:00
                    [state] => 0
                    [operating_system] => ["unx"]
                    [databases_mainframe] => ["db2"]
                    [databases_server] => ["my"]
                    [next_message] => My message
                    [aid] => 33
                )

        )

)

…and I'm inretested in the aid (shown in bold). For the update I use a </PHP> tag and tried:

$var = $this->get('{var:save_data3.var.aid}', "-1");
$var = $this->get('{var:save_data3[aid]}', "-1");
$var = $this->get('{var:save_data3.data.aid}', "-1");
$var = $this->get('{var:save_data3.data[aid]}', "-1");

…and I tried the same with…
​

$var = $this->data('{var:save_data3.var.aid}', "-1");
$var = $this->data('{var:save_data3[aid]}', "-1");
$var = $this->data('{var:save_data3.data.aid}', "-1");
$var = $this->data('{var:save_data3.data[aid]}', "-1");

…and in each case I received -1.
​
Any clue?
​
Thank you in advance,
Axel.

Thanks very much!