pocketmine\block\Liquid::onUpdate PHP Method

    public function onUpdate($type)
    {
        if ($type === Level::BLOCK_UPDATE_NORMAL) {
            $this->checkForHarden();
            $this->getLevel()->scheduleUpdate($this, $this->tickRate());
        } elseif ($type === Level::BLOCK_UPDATE_SCHEDULED) {
            if ($this->temporalVector === null) {
                $this->temporalVector = new Vector3(0, 0, 0);
            }
            $decay = $this->getFlowDecay($this);
            $multiplier = $this instanceof Lava ? 2 : 1;
            $flag = true;
            if ($decay > 0) {
                $smallestFlowDecay = -100;
                $this->adjacentSources = 0;
                $smallestFlowDecay = $this->getSmallestFlowDecay($this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y, $this->z - 1)), $smallestFlowDecay);
                $smallestFlowDecay = $this->getSmallestFlowDecay($this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y, $this->z + 1)), $smallestFlowDecay);
                $smallestFlowDecay = $this->getSmallestFlowDecay($this->level->getBlock($this->temporalVector->setComponents($this->x - 1, $this->y, $this->z)), $smallestFlowDecay);
                $smallestFlowDecay = $this->getSmallestFlowDecay($this->level->getBlock($this->temporalVector->setComponents($this->x + 1, $this->y, $this->z)), $smallestFlowDecay);
                $k = $smallestFlowDecay + $multiplier;
                if ($k >= 8 or $smallestFlowDecay < 0) {
                    $k = -1;
                }
                if (($topFlowDecay = $this->getFlowDecay($this->level->getBlock($this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y + 1, $this->z))))) >= 0) {
                    if ($topFlowDecay >= 8) {
                        $k = $topFlowDecay;
                    } else {
                        $k = $topFlowDecay | 0x8;
                    }
                }
                if ($this->adjacentSources >= 2 and $this instanceof Water) {
                    $bottomBlock = $this->level->getBlock($this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y - 1, $this->z)));
                    if ($bottomBlock->isSolid()) {
                        $k = 0;
                    } elseif ($bottomBlock instanceof Water and $bottomBlock->getDamage() === 0) {
                        $k = 0;
                    }
                }
                if ($this instanceof Lava and $decay < 8 and $k < 8 and $k > 1 and mt_rand(0, 4) !== 0) {
                    $k = $decay;
                    $flag = false;
                }
                if ($k !== $decay) {
                    $decay = $k;
                    if ($decay < 0) {
                        $this->getLevel()->setBlock($this, new Air(), true);
                    } else {
                        $this->getLevel()->setBlock($this, Block::get($this->id, $decay), true);
                        $this->getLevel()->scheduleUpdate($this, $this->tickRate());
                    }
                } elseif ($flag) {
                    //$this->getLevel()->scheduleUpdate($this, $this->tickRate());
                    //$this->updateFlow();
                }
            } else {
                //$this->updateFlow();
            }
            $bottomBlock = $this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y - 1, $this->z));
            if ($bottomBlock->canBeFlowedInto() or $bottomBlock instanceof Liquid) {
                if ($this instanceof Lava and $bottomBlock instanceof Water) {
                    $this->getLevel()->setBlock($bottomBlock, Block::get(Item::STONE), true);
                    $this->triggerLavaMixEffects($bottomBlock);
                    return;
                }
                if ($decay >= 8) {
                    //$this->getLevel()->setBlock($bottomBlock, Block::get($this->id, $decay), true);
                    //$this->getLevel()->scheduleUpdate($bottomBlock, $this->tickRate());
                    $this->flowIntoBlock($bottomBlock, $decay);
                } else {
                    //$this->getLevel()->setBlock($bottomBlock, Block::get($this->id, $decay + 8), true);
                    //$this->getLevel()->scheduleUpdate($bottomBlock, $this->tickRate());
                    $this->flowIntoBlock($bottomBlock, $decay | 0x8);
                }
            } elseif ($decay >= 0 and ($decay === 0 or !$bottomBlock->canBeFlowedInto())) {
                $flags = $this->getOptimalFlowDirections();
                $l = $decay + $multiplier;
                if ($decay >= 8) {
                    $l = 1;
                }
                if ($l >= 8) {
                    $this->checkForHarden();
                    return;
                }
                if ($flags[0]) {
                    $this->flowIntoBlock($this->level->getBlock($this->temporalVector->setComponents($this->x - 1, $this->y, $this->z)), $l);
                }
                if ($flags[1]) {
                    $this->flowIntoBlock($this->level->getBlock($this->temporalVector->setComponents($this->x + 1, $this->y, $this->z)), $l);
                }
                if ($flags[2]) {
                    $this->flowIntoBlock($this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y, $this->z - 1)), $l);
                }
                if ($flags[3]) {
                    $this->flowIntoBlock($this->level->getBlock($this->temporalVector->setComponents($this->x, $this->y, $this->z + 1)), $l);
                }
            }
            $this->checkForHarden();
        }
    }