Pop\Image\Svg::setGradient PHP Метод

    public function setGradient($index = null)
    {
        if (null !== $index && array_key_exists($index, $this->gradients)) {
            $this->curGradient = $index;
        } else {
            $this->curGradient = null;
        }
        return $this;
    }

 public function testGradients()
 {
     $s = new Svg('graph.svg', '640px', '480px');
     $s->addGradient(new Rgb(255, 0, 0), new Rgb(0, 0, 255));
     $s->addGradient(new Rgb(255, 0, 0), new Rgb(0, 0, 255), Svg::VERTICAL);
     $s->addGradient(new Rgb(255, 0, 0), new Rgb(0, 0, 255), Svg::RADIAL);
     $s->setGradient(0);
     $this->assertEquals(640, $s->getWidth());
 }