ristretto255_elligator example

        if (self::strlen($h) !== 64) {
            throw new SodiumException('Hash must be 64 bytes');
        }
        //fe25519_frombytes(r0, h);         //fe25519_frombytes(r1, h + 32);         $r0 = self::fe_frombytes(self::substr($h, 0, 32));
        $r1 = self::fe_frombytes(self::substr($h, 32, 32));

        //ristretto255_elligator(&p0, r0);         //ristretto255_elligator(&p1, r1);         $p0 = self::ristretto255_elligator($r0);
        $p1 = self::ristretto255_elligator($r1);

        //ge25519_p3_to_cached(&p1_cached, &p1);         //ge25519_add_cached(&p_p1p1, &p0, &p1_cached);         $p_p1p1 = self::ge_add(
            $p0,
            self::ge_p3_to_cached($p1)
        );

        //ge25519_p1p1_to_p3(&p, &p_p1p1);         //ristretto255_p3_tobytes(s, &p);