if ($this->grid_depth != DEPTH_BACK) {
                // Draw axis and grid
                for ($i = 0, $a = M_PI / 2; $i < $nbrpnts; ++$i, $a += $astep) {
                    $this->axis->Stroke($this->posy, $a, $grid[$i], $this->axis_title[$i], $i == 0);
                }