public function data(string $action = '', bool $allow_dimensions = false)
    {
        $action = $action ?: $this->action;

        if (!$this->action) {
            return; // Not applicable.
        } elseif ($action !== $this->action) {
            return; // Not applicable.
        } elseif (!isset($_REQUEST[$this->data_var])) {
            return; // Not applicable.
        }
        $data = $_REQUEST[$this->data_var];

        if (is_object($data)) {
            $data = (array) $data;
        }
        $data = $this->c::removeKey($data, '___ignore');
        // Removes keys needed to make forms submit an empty array.

        if (!$allow_dimensions && is_array($data)) {
            $data = array_map('strval', $data);
        }
        $data = $this->c::unslash($data);
        $data = $this->c::mbTrim($data);

        return $data;
    }