Normlaize polskich znaków

/**
 * Description of NormalizeNoneLatinCharacters
 *
 * @author Grzegorz Tarka
 */
class NormalizeNotPolishLetters {

    /**
     * normalize
     * 
     * @param string $string
     * 
     * @return string|null
     */
    public static function normalize(?string $string): ?string {

        $table = [
            'Š' => 'S', 'š' => 's', 'Đ' => 'Dj', 'đ' => 'dj', 'Ž' => 'Z', 'ž' => 'z', 'Č' => 'C', 'č' => 'c',
            'À' => 'A', 'Á' => 'A', 'Â' => 'A', 'Ã' => 'A', 'Ä' => 'A', 'Å' => 'A', 'Æ' => 'A', 'Ç' => 'C', 'È' => 'E', 'É' => 'E',
            'Ê' => 'E', 'Ë' => 'E', 'Ì' => 'I', 'Í' => 'I', 'Î' => 'I', 'Ï' => 'I', 'Ñ' => 'N', 'Ô' => 'O',
            'Õ' => 'O', 'Ö' => 'O', 'Ø' => 'O', 'Ù' => 'U', 'Ú' => 'U', 'Û' => 'U', 'Ü' => 'U', 'Ý' => 'Y', 'Þ' => 'B', 'ß' => 'Ss',
            'à' => 'a', 'á' => 'a', 'â' => 'a', 'ã' => 'a', 'ä' => 'a', 'å' => 'a', 'æ' => 'a', 'ç' => 'c', 'è' => 'e', 'é' => 'e',
            'ê' => 'e', 'ë' => 'e', 'ì' => 'i', 'í' => 'i', 'î' => 'i', 'ï' => 'i', 'ð' => 'o', 'ñ' => 'n',
            'ô' => 'o', 'õ' => 'o', 'ö' => 'o', 'ø' => 'o', 'ù' => 'u', 'ú' => 'u', 'û' => 'u', 'ý' => 'y', 'ý' => 'y', 'þ' => 'b',
            'ÿ' => 'y', 'Ŕ' => 'R', 'ŕ' => 'r', "ò" => 'ó', 'Ò' => 'Ó', 'ė' => 'e', 'Ė' => 'E'
        ];

        return strtr($string, $table);
    }

}