Error with my first plugin help!

Error
22.09 16:54:39 [Server] INFO Fatal error: Declaration of KnockbackM\Main:nCommand(KnockbackM\Command $cmd, KnockbackM\CommandSender $sender, array $args, $label) must be compatible with pocketmine\command\CommandExecutor:nCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $command, string $label, array $args): bool in /plugins/KnockbackM/src/KnockbackM/Main.php on line 12


LINE 12 =

PHP:

class Main extends PluginBase implements Listener{


Code

PHP:

<?php
namespace KnockbackM;

use pocketmine\event\Event;
use pocketmine\event\entity\EntityDamageByEntityEvent;
use pocketmine\event\entity\EntityDamageEvent;
use pocketmine\Server;
use pocketmine\Player;
use pocketmine\plugin\PluginBase;
use pocketmine\event\Listener;

class Main extends PluginBase implements Listener{

  public function onEnable() {
    $this->getServer()->getPluginManager()->registerEvents($this,$this);
  }

  public $knockback = 0.4;

  public function onCommand(Command $cmd, CommandSender $sender, array $args, $label) {
    if($cmd->getName() == "kb") {
      $event->setKnockback($args[0]);
      $sender->sendMessage("Knockback Set!");
    }
  }

  public function onDamage(EntityDamageEvent $event) {
    if($event instanceof EntityDamageByEntityEvent){
      $event->setKnockback(1.0);
    }
  }
}


 

Sorry, like I said im new to this. This is my first real plugin. Didnt know that I didnt just have to change api in plugin.yml. Thanks

 

Read the thread Thunder gave you. Beginners should understand it. If you don't, here's how to fix it:

Find the line in your code:

PHP:

public function onCommand(Command $cmd, CommandSender $sender, array $args, $label)


It must be compatible with:

PHP:

public function onCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $cmd, string $label, array $args): bool


That means, your line needs to exactly look like this (if you used the use keyword on the CommandSender and Command class, you can remove the pocketmine\command\ in-front of those).
Look here to get an idea.