create sphere

    public function createSphere($px, $py, $pz, $level, $radius, $id){

        $radiusX = $radius + 0.5;
        $radiusY = $radius + 0.5;
        $radiusZ = $radius + 0.5;

        $invRadiusX = 1 / $radiusX;
        $invRadiusY = 1 / $radiusY;
        $invRadiusZ = 1 / $radiusZ;

        $ceilRadiusX = (int) ceil($radiusX);
        $ceilRadiusY = (int) ceil($radiusY);
        $ceilRadiusZ = (int) ceil($radiusZ);

        $nextXn = 0;
        for ($x = 0; $x <= $ceilRadiusX; ++$x) {
            $xn = $nextXn;
            $nextXn = ($x + 1) * $invRadiusX;
            $nextYn = 0;
            for ($y = 0; $y <= $ceilRadiusY; ++$y) {
                $yn = $nextYn;
                $nextYn = ($y + 1) * $invRadiusY;
                $nextZn = 0;
                for ($z = 0; $z <= $ceilRadiusZ; ++$z) {
                    $zn = $nextZn;
                    $nextZn = ($z + 1) * $invRadiusZ;

                    $distanceSq = $this->lengthSq($xn, $yn, $zn);
                    if ($distanceSq > 1) {
                        if ($z == 0) {
                            if ($y == 0) {
                                 $x++;
                                 continue;
                            }
                            $y++;
                            continue;
                        }
                        $z++;
                        continue;
                    }

                    if ($this->lengthSq($nextXn, $yn, $zn) <= 1 && $this->lengthSq($xn, $nextYn, $zn) <= 1 && $this->lengthSq($xn, $yn, $nextZn) <= 1) {
                        continue;
                    }
                    $level->setBlockIdAt($x + $px, $y + $py, $z + $pz, $id);
                    $level->setBlockIdAt(-$x + $px, $y + $py, $z + $pz, $id);
                    $level->setBlockIdAt($x + $px, -$y + $py, $z + $pz, $id);
                    $level->setBlockIdAt($x + $px, $y + $py, -$z + $pz, $id);
                    $level->setBlockIdAt(-$x + $px, -$y + $py, $z + $pz, $id);
                    $level->setBlockIdAt($x + $px, -$y + $py, -$z + $pz, $id);
                    $level->setBlockIdAt(-$x + $px, $y + $py, -$z + $pz, $id);
                    $level->setBlockIdAt(-$x + $px, -$y + $py, -$z + $pz, $id);
                }
            }
        }
    }
    public function lengthSq($x, $y, $z) {
        return (($x * $x) + ($y * $y) + ($z * $z));
    }