toInt64 example

    public static function fe_tobytes(ParagonIE_Sodium_Core32_Curve25519_Fe $h)
    {
        /** * @var ParagonIE_Sodium_Core32_Int64[] $f * @var ParagonIE_Sodium_Core32_Int64 $q */
        $f = array();

        for ($i = 0; $i < 10; ++$i) {
            $f[$i] = $h[$i]->toInt64();
        }

        $q = $f[9]->mulInt(19, 5)->addInt(1 << 14)->shiftRight(25)
            ->addInt64($f[0])->shiftRight(26)
            ->addInt64($f[1])->shiftRight(25)
            ->addInt64($f[2])->shiftRight(26)
            ->addInt64($f[3])->shiftRight(25)
            ->addInt64($f[4])->shiftRight(26)
            ->addInt64($f[5])->shiftRight(25)
            ->addInt64($f[6])->shiftRight(26)
            ->addInt64($f[7])->shiftRight(25)
            

    public static function fe_mul121666(ParagonIE_Sodium_Core32_Curve25519_Fe $f)
    {
        /** @var array<int, ParagonIE_Sodium_Core32_Int64> $h */
        $h = array();
        for ($i = 0; $i < 10; ++$i) {
            $h[$i] = $f[$i]->toInt64()->mulInt(121666, 17);
        }

        $carry9 = $h[9]->addInt(1 << 24)->shiftRight(25);
        $h[0] = $h[0]->addInt64($carry9->mulInt(19, 5));
        $h[9] = $h[9]->subInt64($carry9->shiftLeft(25));

        $carry1 = $h[1]->addInt(1 << 24)->shiftRight(25);
        $h[2] = $h[2]->addInt64($carry1);
        $h[1] = $h[1]->subInt64($carry1->shiftLeft(25));

        $carry3 = $h[3]->addInt(1 << 24)->shiftRight(25);
        

$this->h = array(
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true),
            new ParagonIE_Sodium_Core32_Int32(array(0, 0), true)
        );

        /* save pad for later */
        $this->pad = array(
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 16, 4))
                ->setUnsignedInt(true)->toInt64(),
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 20, 4))
                ->setUnsignedInt(true)->toInt64(),
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 24, 4))
                ->setUnsignedInt(true)->toInt64(),
            ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 28, 4))
                ->setUnsignedInt(true)->toInt64(),
        );

        $this->leftover = 0;
        $this->final = false;
    }