pocketmine\Player::checkGroundState PHP Method

    protected function checkGroundState($movX, $movY, $movZ, $dx, $dy, $dz)
    {
        if (!$this->onGround or $movY != 0) {
            $bb = clone $this->boundingBox;
            $bb->maxY = $bb->minY + 0.5;
            $bb->minY -= 1;
            if (count($this->level->getCollisionBlocks($bb, true)) > 0) {
                $this->onGround = true;
            } else {
                $this->onGround = false;
            }
        }
        $this->isCollided = $this->onGround;
    }