Contao\FormSelectMenu::validate PHP Метод

    public function validate()
    {
        $mandatory = $this->mandatory;
        $options = $this->getPost($this->strName);
        // Check if there is at least one value
        if ($mandatory && is_array($options)) {
            foreach ($options as $option) {
                if (strlen($option)) {
                    $this->mandatory = false;
                    break;
                }
            }
        }
        $varInput = $this->validator($options);
        // Check for a valid option (see #4383)
        if (!empty($varInput) && !$this->isValidOption($varInput)) {
            $this->addError(sprintf($GLOBALS['TL_LANG']['ERR']['invalid'], is_array($varInput) ? implode(', ', $varInput) : $varInput));
        }
        // Add class "error"
        if ($this->hasErrors()) {
            $this->class = 'error';
        } else {
            $this->varValue = $varInput;
        }
        // Reset the property
        if ($mandatory) {
            $this->mandatory = true;
        }
    }