pocketmine\entity\Minecart::forwardOnRail PHP Method

    private function forwardOnRail(Player $player)
    {
        if ($this->direction === -1) {
            $candidateDirection = $player->getDirection();
        } else {
            $candidateDirection = $this->direction;
        }
        $rail = $this->getCurrentRail();
        if ($rail !== null) {
            $railType = $rail->getDamage();
            $nextDirection = $this->getDirectionToMove($railType, $candidateDirection);
            if ($nextDirection !== -1) {
                $this->direction = $nextDirection;
                $moved = $this->checkForVertical($railType, $nextDirection);
                if (!$moved) {
                    return $this->moveIfRail();
                } else {
                    return true;
                }
            } else {
                $this->direction = -1;
                // Was not able to determine direction to move, so wait for player to look in valid direction
            }
        } else {
            // Not able to find rail
            $this->state = Minecart::STATE_INITIAL;
        }
        return false;
    }