function setIteratorIndex($firstLayer)
{
$imagick = new \Imagick(realpath("images/LayerTest.psd"));
$output = new \Imagick();
$imagick->setIteratorIndex($firstLayer);
do {
$output->addImage($imagick->getimage());
} while ($imagick->nextImage());
$merged = $output->mergeImageLayers(\Imagick::LAYERMETHOD_MERGE);
$merged->setImageFormat('png');
header("Content-Type: image/png");
echo $merged->getImageBlob();
}