src/ValidLanguage.php
public function valid($language)
    {
        if (empty($language)) {
            return false;
        }
        if ($language == 'en' || $language == 'de' || $language == 'pl' || $language == 'ru') {
            return true;
        }
        return false;
    }
public function valid($language)
    {
        if (empty($language)) {
            return false;
        }
        if ($language == 'en' || $language == 'de' || $language == 'pl' || $language == 'ru') {
            return true;
        }
        return false;
    }
public function valid ( $ language ) { if ( empty ( $ language ) ) { return false ; } if ( $ language == 'en' || $ language == 'de' || $ language == 'pl' || $ language == 'ru' ) { return true ; } return false ; }
validation of language

@param $language
@return bool
validation of language