The light in the new world is like hell

how to make the lighting in my created world be like hell? MCPE 1.1.x

PHP:

<?php

namespace Forter\oneblock\island\generator;

use pocketmine\block\Block;
use pocketmine\level\ChunkManager;
use pocketmine\level\generator\biome\{ Biome, BiomeSelector };
use pocketmine\level\generator\Generator;
use pocketmine\level\generator\object\OreType;
use pocketmine\level\generator\populator\{ GroundCover, Ore, Populator };
use pocketmine\level\Level;
use pocketmine\math\Vector3;
use pocketmine\utils\Random;

class NetherGenerator extends Generator{

    protected $level;
    protected $random;


    public function __construct(array $options = []){}

    public function init(ChunkManager $level, Random $random){
        $this->level = $level;
        $this->random = $random;
    }

    public function getSettings(){
        return [];
    }
    
    public function getName(){
        return "ad";
    }

    public function generateChunk($chunkX, $chunkZ){
        $chunk = $this->level->getChunk($chunkX, $chunkZ);
        if ($chunkX == 0 && $chunkZ == 0) $chunk->setBlockId(8, 127, 8, 87);
        for($x = 0; $x < 16; ++$x){
            for($z = 0; $z < 16; ++$z){
                for($y = 0; $y < 128; ++$y){
                    $biome = Biome::getBiome(Biome::HELL);
                    $chunk->setBiomeId($x, $z, $biome->getId());
                    $chunk->setBlockLight($x, $y + 1, $z, 15);//does not work
                }
            }
        }
        $chunk->setGenerated();
    }

    public function populateChunk($chunkX, $chunkZ){
        $this->random->setSeed(0xdeadbeef ^ ($chunkX << 8) ^ $chunkZ ^ $this->level->getSeed());
        //$centerOfChunk = new Vector3($chunkX * 16 - 8, 128, $chunkZ * 16 - 8);     
    }
    
    public function getSpawn(): Vector3{
        return new Vector3(264, 255, 264);
    }
}