pocketmine\item\Bucket::onActivate PHP Method

    public function onActivate(Level $level, Player $player, Block $block, Block $target, $face, $fx, $fy, $fz)
    {
        $targetBlock = Block::get($this->meta);
        if ($targetBlock instanceof Air) {
            if ($target instanceof Liquid and $target->getDamage() === 0) {
                $result = clone $this;
                $id = $target->getId();
                if ($id == self::STILL_WATER) {
                    $id = self::WATER;
                }
                if ($id == self::STILL_LAVA) {
                    $id = self::LAVA;
                }
                $result->setDamage($id);
                $player->getServer()->getPluginManager()->callEvent($ev = new PlayerBucketFillEvent($player, $block, $face, $this, $result));
                if (!$ev->isCancelled()) {
                    $player->getLevel()->setBlock($target, new Air(), true, true);
                    if ($player->isSurvival()) {
                        $player->getInventory()->setItemInHand($ev->getItem());
                    }
                    return true;
                } else {
                    $player->getInventory()->sendContents($player);
                }
            }
        } elseif ($targetBlock instanceof Liquid) {
            $result = clone $this;
            $result->setDamage(0);
            $player->getServer()->getPluginManager()->callEvent($ev = new PlayerBucketEmptyEvent($player, $block, $face, $this, $result));
            if (!$ev->isCancelled()) {
                //Only disallow water placement in the Nether, allow other liquids to be placed
                //In vanilla, water buckets are emptied when used in the Nether, but no water placed.
                if (!($player->getLevel()->getDimension() === Level::DIMENSION_NETHER and $targetBlock->getID() === self::WATER)) {
                    $player->getLevel()->setBlock($block, $targetBlock, true, true);
                }
                if ($player->isSurvival()) {
                    $player->getInventory()->setItemInHand($ev->getItem());
                }
                return true;
            } else {
                $player->getInventory()->sendContents($player);
            }
        }
        return false;
    }