How to get value from the field from custom php code

Hello, I'm trying to get value of a field 'checkbox104' from custom php code:

$check_box_get = $this->get('checkbox104', 0);
$check_box_data = $this->data('checkbox104', 0);

if ($check_box_data != 1) {
echo $check_box_get;
echo $check_box_data;
$this->data('checkbox104', 1, true);
return $article_note;}
else {
echo $check_box_get;
echo $check_box_data;
return 0;}
​
but it always returns default value with $this->get or with $this->data.
​
​

Array
(
    [Itemid] => 1176
    [option] => com_content
    [view] => article
    [id] => 232
    [lang] => en
    [catid] => 2
    [_ga] => GA1.2.108603241.1608997853
    [fcba6eff3bcff11268aeb9d73ebac6b2] => b411edc9d98f579395e2c42ed9946e63
    [6fc35e6b52a32ae9a673b76d96b4731e] => 945075db290ed8e824ec8c16dc2371be
    [joomsef_lang] => en
    [_gid] => GA1.2.1966733552.1609255125
    [language] => en-GB
    [_gat] => 1
    [checkbox104] => 1
)

Array
(
    [set_checkbox] => Array
        (
            [returned] => 
            [var] => 
        )

    [default_service_type_php] => Array
        (
            [returned] => transfer_indi
            [var] => transfer_indi
        )

    [default_service_name_php] => Array
        (
            [returned] => request-form-all-services
            [var] => request-form-all-services
        )

    [check_box] => Array
        (
            [returned] => 
            [var] => 
        )

)