How to change name of the world?

The title says all. I need to know how to change the name of the world.
p/s: I mean not rename the folder world

 

usually i create a new world(of course world name is not same)
and open created world, copy lavel.dat, then paste it in you want to change world name.
after pasted, rename folder, and reset default spawn coordinates.

 

you can use a nbt editor and edit the level name attribute in level.dat. I do strongly advisee you to not blindly copy level.dat from fresh levels, because there might be important data in the level.dat.
NBT editors can be found here: Windows / Linux Mac Github NBTedit

 

What if we want to do it using code?

 

well, the level would have to be unloaded and then you can do this:

PHP:

$levelPath = "/path/to/your/level";
$newName = "/path/to/your/level";

$nbt = new pocketmine\nbt\BigEndianNBTStream();
$levelData = $nbt->readCompressed(file_get_contents($levelPath . "level.dat"));
$levelData = $levelData->getCompoundTag("Data");
$oldName = $levelData->getString("LevelName");
$levelData->setString("LevelName", $newName);
$nbt = new BigEndianNBTStream();
file_put_contents($levelPath . "level.dat", $nbt->writeCompressed(new CompoundTag("", [$levelData])));
echo("Renamed $oldName to $newName");