ConquerorSoft / my_first_library

     * @return string

     * @throws \Exception

     */

    public function encodeString($string)

    {

        $string=strtolower($string);

        $src="abcdefghijklmnopqrstuvwxyz0123456789 ";

        $dst="jklmnopqrstuvwxyz0123456789abcdefghi ";

        for ($i=0; $i<strlen($string); $i++) {

            $pos=strpos($src, $string[$i]);

            if ($pos===false) {

                throw new \Exception("Please provide only numbers and alphanumerical characters");

            }

            $string[$i]=$dst[$pos];

        }

        return $string;

    }

    /**

     * Decodes a string by a simple shift of characters

     * @return string

     * @throws \Exception

     */

    public function decodeString($string)

    {

        $string=strtolower($string);

        $src="jklmnopqrstuvwxyz0123456789abcdefghi ";

        $dst="abcdefghijklmnopqrstuvwxyz0123456789 ";

        for ($i=0; $i<strlen($string); $i++) {

            $pos=strpos($src, $string[$i]);

            if ($pos===false) {

                throw new \Exception("Please provide only numbers and alphanumerical characters");

            }

            $string[$i]=$dst[$pos];

        }

        return $string;

    }

}