PHP Imagick - Watermark images

$image = new Imagick();
$image->readImage($source);

// Open the watermark
$watermark = new Imagick();
$watermark->readImage($logo);

// Overlay the watermark on the original image (bottom - right, margin: 5px)
$image->compositeImage($watermark, imagick::COMPOSITE_OVER, $image->getImageWidth() - $watermark->getImageWidth() -5, $image->getimageheight() - $watermark->getImageHeight() - 5);

// send the result to the browser
header("Content-Type: image/" . $image->getImageFormat());
echo $image;