public static function addOrRemoveS($word)
    {
        $arrayOfCharInTable = str_split($word);

        if ($arrayOfCharInTable[count($arrayOfCharInTable) - 1] === 's') {
            array_pop($arrayOfCharInTable);
            $word = implode($arrayOfCharInTable);
        } else {
            $word .= 's';
        }

        return $word;
    }