Example

function gradientReflection()
{
    $im = new \Imagick(realpath('images/sample.png'));
    
    $reflection = clone $im;

    $reflection->flipImage();

    $reflection->cropImage($im->getImageWidth(), $im->getImageHeight() * 0.75, 0, 0);

    $gradient = new \Imagick();
    $gradient->newPseudoImage(
        $reflection->getImageWidth(),
        $reflection->getImageHeight(),
        //Putting spaces in the rgba string is bad
        'gradient:rgba(255,0,255,0.6)-rgba(255,255,0,0.99)'
    );

    $reflection->compositeimage(
        $gradient,
        \Imagick::COMPOSITE_DSTOUT,
        0, 0
    );

    $canvas = new \Imagick();
    $canvas->newImage($im->getImageWidth(), $im->getImageHeight() * 1.75, new \ImagickPixel('rgba(255, 255, 255, 0)'));
    $canvas->compositeImage($im, \Imagick::COMPOSITE_BLEND, 0, 0);
    $canvas->setImageFormat('png');
    $canvas->compositeImage($reflection, \Imagick::COMPOSITE_BLEND, 0, $im->getImageHeight());

    $canvas->stripImage();
    $canvas->setImageFormat('png');
    header('Content-Type: image/png');
    echo $canvas;
}