Example

function mosaicImages()
{
    $imagick = new \Imagick();
    $mosaicWidth = 500;
    $mosaicHeight = 500;
    
    $imagick->newimage($mosaicWidth, $mosaicHeight, 'red');

    $images = [
        "../public/images/Biter_500.jpg",
        "../public/images/SydneyPeople_400.jpg",
        "../public/images/Skyline_400.jpg",
    ];

    $positions = [
        [50, 300],
        [200, 125],
        [25, 50],
    ];
    
    $count = 0;

    foreach ($images as $image) {
        $nextImage = new \Imagick(realpath($image));
        $nextImage->resizeimage(300, 300, \Imagick::FILTER_LANCZOS, 1.0, true);

        $nextImage->setImagePage(
            $nextImage->getImageWidth(),
            $nextImage->getImageHeight(),
            $positions[$count][0],
            $positions[$count][1]
        );
        
        $imagick->addImage($nextImage);
        $count++;
    }

    $result = $imagick->mosaicImages();
    $result->setImageFormat('png');

    $result->cropImage(
        $mosaicWidth,
        $mosaicHeight,
        0, 0
    );

    header("Content-Type: image/png");
    echo $result->getImageBlob();
}