I need cut a circle map

I have a big map. And I would like to make this map circle.
What I need do?
I think, that I need create function, witch will delete excess chunks, and after that, I need delete other unnecessary block. Is it true?)

 

I am trying
I will write the results later

 

Now i have this, but chunks don't change :c

PHP:

    public function cuteCircleMap($level) {
        # Map radius, in block's
        $radius = 1000;
        # Chunk count
        $mapChunks = array('x' => 128,
                           'y' => 128);
        # Дальше все будет вычисляться само
        $spawnPoint = array('x' => $mapChunks['x'] * 8, // Умножаем на 16, делим на 2
                            'y' => $mapChunks['y'] * 8);
        for ($chunkX = 0; $chunkX < $mapChunks['x']; $chunkX++) {
            for ($chunkY = 0; $chunkY < $mapChunks['y']; $chunkY++) {

                $level->loadChunk($chunkX, $chunkY, false);
                // Позиция центра чанка
                $fixedChunkPosition = array('x' => $chunkX * 16 + 8,
                                            'y' => $chunkY * 16 + 8);
                $distance = sqrt(pow($spawnPoint['x'] - $fixedChunkPosition['x'],2) +
                                 pow($spawnPoint['y'] - $fixedChunkPosition['y'],2));
                echo("Chunk ".$chunkX .":". $chunkY." distance:".round($distance)." ".
                     "progress:".(round(($chunkY + $chunkX*$mapChunks['x'])*100/($mapChunks['x']*$mapChunks['y'])))."%\n");
                if ($distance > $radius) {
                    $newChunk = Chunk::getEmptyChunk($chunkX, $chunkY);
                    $level->setChunk($chunkX, $chunkY, $newChunk);
                }
                $level->unloadChunk($chunkX, $chunkY, true);
            }
        }
    }

Can I delete chunks? I don't find how can I do this in pmmp :c

 

SUCCESSFULLY!!!
2048 * 2048 for 30 seconds :3
Yeea

PHP:

    public function cuteCircleMap($level) {
        # Радиус вырезаемой карты, в блоках
        $radius = 1024;
        # Количество чанков
        $mapChunks = array('x' => 128,
                           'y' => 128);
        # Дальше все будет вычисляться само
        $spawnPoint = array('x' => $mapChunks['x'] * 8, // Умножаем на 16, делим на 2
                            'y' => $mapChunks['y'] * 8);
        for ($chunkX = 0; $chunkX < $mapChunks['x']; $chunkX++) {
            for ($chunkY = 0; $chunkY < $mapChunks['y']; $chunkY++) {
                // Позиция центра чанка
                $fixedChunkPosition = array('x' => $chunkX * 16 + 8,
                                            'y' => $chunkY * 16 + 8);
                $distance = sqrt(pow($spawnPoint['x'] - $fixedChunkPosition['x'],2) +
                                 pow($spawnPoint['y'] - $fixedChunkPosition['y'],2));
                echo("Chunk ".$chunkX .":". $chunkY." distance:".round($distance)." ".
                     "progress:".(round(($chunkY + $chunkX*$mapChunks['x'])*100/($mapChunks['x']*$mapChunks['y'])))."%\n");

                if ($distance - 12 > $radius) {
                    $newChunk = Chunk::getEmptyChunk($chunkX, $chunkY);
                    $newChunk->setGenerated(true);
                    $level->getProvider()->setChunk($chunkX, $chunkY, $newChunk);
                    $level->getProvider()->saveChunk($chunkX, $chunkY);
                }
                if (abs($distance - $radius) < 12) {
                    $chunk = $level->getChunk($chunkX, $chunkY);
                    for ($x = $chunkX * 16; $x < $chunkX * 16 + 16; $x++) {
                        for ($y = $chunkY * 16; $y < $chunkY * 16 + 16; $y++) {
                            $distance = sqrt(pow($spawnPoint['x'] - $x,2) + pow($spawnPoint['y'] - $y,2));
                            if ($distance > $radius) {
                                for ($z = 0; $z < 256; $z++) {
                                    $chunk->setBlockId($x - $chunkX * 16, $z, $y - $chunkY * 16, 0);
                                }
                            }
                        }
                    }
                    $level->unloadChunk($chunkX, $chunkY);
                }
            }
        }
    }