php - How to push a new value to a cached array in fat-free-framework?

one text

I have a fat-free-framework application where I need to cache API calls, in order to move them later to the database in a Cron job:

<?php

class ApiCallRepository extends BaseRepository
{
    function __construct(ApiCall $model)
    {
        $this->f3 = Base::instance();
        parent::__construct($model);
    }

    public function cache($url, $body, $response)
    {
        if(!$this->f3->exists('API_CALLS')) {
            $this->f3->set('API_CALLS', [], 86400);
        }

        // die(var_export($this->f3->get("API_CALLS"), true));
        /*
            array (
            )
        */
    
        $createdAt = date("Y-m-d H:i:s");
        $api_log = [
            'url' => $url,
            'body' => $body,
            'response' => $response,
            'createdAt' => $createdAt
        ];

        $api_log = json_encode($api_log);
        $this->f3->push("API_CALLS", $api_log);

        die(var_export($this->f3->get("API_CALLS"), true));
        /*
            array (
            0 =>
            '{
                 "url":"https://api-resource.com/users",
                 "body":"",
                 "response":"{"data": {}}"
                 "createdAt":"2022-08-25 14:05:13"
             }'
            )
        */
    }

    public function create($url, $body, $response)
    {
        $this->model->create($url, $body, $response);
    }
}

I am using Redis as my cache driver, and the new log is being pushed to the array successfully, but it doesn't seem to be stored in the cache, because when I try to var_dump the contents of 'API_CALLS' in a different request, it shows an empty array

what could be the problem?