I dont know what's wrong

06:09:47] [Server thread/CRITICAL]: ErrorException: "Use of undefined constant Titan - assumed 'Titan' (this will throw an Error in a future version of PHP)" (EXCEPTION) in "plugins/Rank-Vouchers-master/src/RankVoucher/Main" at line 102
[06:09:47] [Server thread/DEBUG]: #0 plugins/Rank-Vouchers-master/src/RankVoucher/Main(102): pocketmine\utils\Utils::errorExceptionHandler(integer 2, string[103] Use of undefined constant Titan - assumed 'Titan' (this will throw an Error in a, string[87] /storage/emulated/0/PocketMine-MP/plugins/Rank-Vouchers-master/src/RankVoucher/M, integer 102, array[3])
[06:09:47] [Server thread/DEBUG]: #1 src/pocketmine/plugin/MethodEventExecutor(38): RankVoucher\Main->onInteract(object pocketmine\event\player\PlayerInteractEvent)
[06:09:47] [Server thread/DEBUG]: #2 src/pocketmine/plugin/RegisteredListener(98): pocketmine\plugin\MethodEventExecutor->execute(object RankVoucher\Main, object pocketmine\event\player\PlayerInteractEvent)
[06:09:47] [Server thread/DEBUG]: #3 src/pocketmine/event/Event(99): pocketmine\plugin\RegisteredListener->callEvent(object pocketmine\event\player\PlayerInteractEvent)
[06:09:47] [Server thread/DEBUG]: #4 src/pocketmine/level/Level(1919): pocketmine\event\Event->call()
[06:09:47] [Server thread/DEBUG]: #5 src/pocketmine/Player(2417): pocketmine\level\Level->useItemOn(object pocketmine\math\Vector3, object pocketmine\item\Book, integer 4, object pocketmine\math\Vector3, object pocketmine\Player, boolean 1)
[06:09:47] [Server thread/DEBUG]: #6 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(150): pocketmine\Player->handleInventoryTransaction(object pocketmine\network\mcpe\protocol\InventoryTransactionPacket)
[06:09:47] [Server thread/DEBUG]: #7 src/pocketmine/network/mcpe/protocol/InventoryTransactionPacket(158): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleInventoryTransaction(object pocketmine\network\mcpe\protocol\InventoryTransactionPacket)
[06:09:47] [Server thread/DEBUG]: #8 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\InventoryTransactionPacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[06:09:47] [Server thread/DEBUG]: #9 src/pocketmine/network/mcpe/protocol/BatchPacket(123): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\InventoryTransactionPacket)
[06:09:47] [Server thread/DEBUG]: #10 src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter(110): pocketmine\network\mcpe\protocol\BatchPacket->handle(object pocketmine\network\mcpe\PlayerNetworkSessionAdapter)
[06:09:47] [Server thread/DEBUG]: #11 src/pocketmine/Player(3126): pocketmine\network\mcpe\PlayerNetworkSessionAdapter->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[06:09:47] [Server thread/DEBUG]: #12 src/pocketmine/network/mcpe/RakLibInterface(169): pocketmine\Player->handleDataPacket(object pocketmine\network\mcpe\protocol\BatchPacket)
[06:09:47] [Server thread/DEBUG]: #13 vendor/pocketmine/raklib/src/server/ServerHandler(99): pocketmine\network\mcpe\RakLibInterface->handleEncapsulated(string[17] 192.168.0.3 50692, object raklib\protocol\EncapsulatedPacket, integer 0)
[06:09:47] [Server thread/DEBUG]: #14 src/pocketmine/network/mcpe/RakLibInterface(109): raklib\server\ServerHandler->handlePacket()
[06:09:47] [Server thread/DEBUG]: #15 src/pocketmine/network/mcpe/RakLibInterface(99): pocketmine\network\mcpe\RakLibInterface->process()
[06:09:47] [Server thread/DEBUG]: #16 vendor/pocketmine/snooze/src/SleeperHandler(123): pocketmine\network\mcpe\RakLibInterface->pocketmine\network\mcpe\{closure}()
[06:09:47] [Server thread/DEBUG]: #17 vendor/pocketmine/snooze/src/SleeperHandler(85): pocketmine\snooze\SleeperHandler->processNotifications()
[06:09:47] [Server thread/DEBUG]: #18 src/pocketmine/Server(2348): pocketmine\snooze\SleeperHandler->sleepUntil(double 1570860587.5441)
[06:09:47] [Server thread/DEBUG]: #19 src/pocketmine/Server(2205): pocketmine\Server->tickProcessor()
[06:09:47] [Server thread/DEBUG]: #20 src/pocketmine/Server(1784): pocketmine\Server->start()
[06:09:47] [Server thread/DEBUG]: #21 src/pocketmine/PocketMine(275): pocketmine\Server->__construct(object BaseClassLoader, object pocketmine\utils\MainLogger, string[34] /storage/emulated/0/PocketMine-MP/, string[42] /storage/emulated/0/PocketMine-MP/plugins/)
[06:09:47] [Server thread/DEBUG]: #22 src/pocketmine/PocketMine(299): pocketmine\server()
[06:09:47] [Server thread/DEBUG]: #23 (1): require(string[89] phar:///storage/emulated/0/PocketMine-MP/PocketMine-MP.phar/src/pocketmine/Pocke)

 

And we don't know what plugin you're having a problem with. (link?)

 

did you $this->? especially if your consts are defined outside the function with the calling code

 

You probably did something like $player->sendMessage("Hello " . sender->getName() . "!"); forgetting to add a $ before the $sender->getName() part.