Avoid usage of for-loop vars outside of for-loop context

these problems were reported by PHPStan strict rules. They aren't actually bugs, but they could become bugs in the future.

src/pocketmine/level/format/Chunk.php

@@ -411,8 +411,8 @@ class Chunk{
 	 * @return int New calculated heightmap value (0-256 inclusive)
 	 */
 	public function recalculateHeightMapColumn(int $x, int $z) : int{
-		$max = $this->getHighestBlockAt($x, $z);
+		$y = $this->getHighestBlockAt($x, $z);
-		for($y = $max; $y >= 0; --$y){
+		for(; $y >= 0; --$y){
 			if(BlockFactory::$lightFilter[$id = $this->getBlockId($x, $y, $z)] > 1 or BlockFactory::$diffusesSkyLight[$id]){
 				break;
 			}
@@ -438,9 +438,9 @@ class Chunk{
 
 		for($x = 0; $x < 16; ++$x){
 			for($z = 0; $z < 16; ++$z){
+				$y = $maxY;
 				$heightMap = $this->getHeightMap($x, $z);
-
+				for(; $y >= $heightMap; --$y){
-				for($y = $maxY; $y >= $heightMap; --$y){
 					$this->setBlockSkyLight($x, $y, $z, 15);
 				}
 
@@ -805,10 +805,10 @@ class Chunk{
 				//No need to thoroughly prune empties at runtime, this will just reduce performance.
 				continue;
 			}
-			break;
+			return $y;
 		}
 
-		return $y;
+		return -1;
 	}
 
 	/**

src/pocketmine/level/generator/populator/GroundCover.php

@@ -47,7 +47,8 @@ class GroundCover extends Populator{
 					}
 
 					$column = $chunk->getBlockIdColumn($x, $z);
-					for($y = 127; $y > 0; --$y){
+					$y = 127;
+					for(; $y > 0; --$y){
 						if($column[$y] !== "\x00" and !BlockFactory::get(ord($column[$y]))->isTransparent()){
 							break;
 						}

src/pocketmine/level/generator/populator/TallGrass.php

@@ -77,10 +77,10 @@ class TallGrass extends Populator{
 		for($y = 127; $y >= 0; --$y){
 			$b = $this->level->getBlockIdAt($x, $y, $z);
 			if($b !== Block::AIR and $b !== Block::LEAVES and $b !== Block::LEAVES2 and $b !== Block::SNOW_LAYER){
-				break;
+				return $y + 1;
 			}
 		}
 
-		return $y === 0 ? -1 : ++$y;
+		return -1;
 	}
 }

src/pocketmine/level/generator/populator/Tree.php

@@ -83,12 +83,12 @@ class Tree extends Populator{
 		for($y = 127; $y > 0; --$y){
 			$b = $this->level->getBlockIdAt($x, $y, $z);
 			if($b === Block::DIRT or $b === Block::GRASS){
-				break;
+				return $y + 1;
 			}elseif($b !== Block::AIR and $b !== Block::SNOW_LAYER){
 				return -1;
 			}
 		}
 
-		return ++$y;
+		return -1;
 	}
 }

src/pocketmine/network/mcpe/PlayerNetworkSessionAdapter.php

@@ -287,7 +287,8 @@ class PlayerNetworkSessionAdapter extends NetworkSession{
 					if($quoteType === null){
 						$quoteType = $raw[$i];
 					}elseif($raw[$i] === $quoteType){
-						for($backslashes = 0; $backslashes < $i && $raw[$i - $backslashes - 1] === "\\"; ++$backslashes){}
+						$backslashes = 0;
+						for(; $backslashes < $i && $raw[$i - $backslashes - 1] === "\\"; ++$backslashes){}
 						if(($backslashes % 2) === 0){ //unescaped quote
 							$quoteType = null;
 						}