public function validate() : void
    {
        if (null === $this->is_valid) {
            if (null === $this->user_value && null !== $this->default_value) {
                // There is a preset value, and its not being changed
                $this->is_valid = true;
            } elseif (in_array($this->user_value, array_keys($this->options)) && !in_array($this->user_value,
                    $this->disabled)
            ) {
                $this->is_valid = true;
            } elseif ('' == $this->user_value && $this->addBlank && !in_array('', $this->disabled)) {
                $this->is_valid = true;
            } elseif (false == $this->validator) {
                // This field does not get validated
                $this->is_valid = true;
            } else {
                $this->is_valid = false;
                $this->error = 'The provided value is not valid. Please enter a valid value.';
            }
        }

        // Check if the input is different from the default value
        if ($this->is_valid && null !== $this->user_value) {
            $this->is_changed = ($this->default_value != $this->user_value);
        }
    }