spawnToAll error

This is my code:

$player = $sender;
$sender->sendMessage("Spawned a Cow");
$nbt = new CompoundTag("", [
"Pos" => new ListTag("Pos", [
new DoubleTag("", $player->x),
new DoubleTag("", $player->y),
new DoubleTag("", $player->z)
]),
"Motion" => new ListTag("Motion", [
new DoubleTag("", -sin($player->yaw / 180 * M_PI) * cos($player->pitch / 180 * M_PI)),
new DoubleTag("", -sin($player->pitch / 180 * M_PI)),
new DoubleTag("", cos($player->yaw / 180 * M_PI) * cos($player->pitch / 180 * M_PI))
]),
"Rotation" => new ListTag("Rotation", [
new FloatTag("", $player->yaw),
new FloatTag("", $player->pitch)
]),
]);

$entity = Entity::createEntity("Cow", $player->getLevel(), $nbt, $player);

$entity->spawnToAll();



And this is the error:

Call to a meber function spawnToAll() on null

 

Do you know where my misstake is ?

 

You will need to register your Entity first: https://github.com/pmmp/PocketMine-...170980b/src/pocketmine/entity/Entity.php#L389

 

Can you give me a example ?

 

There is an new error:
Call to a meber function register() on null

 

I fixed it