Example

function montageImage($montageType)
{
    $draw = new \ImagickDraw();
    $draw->setStrokeColor('black');
    $draw->setFillColor('white');
 
    $draw->setStrokeWidth(1);
    $draw->setFontSize(24);

    $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",
    ];

    $count = 0;
    
    foreach ($images as $image) {
        $nextImage = new \Imagick(realpath($image));
        
        $count++;
        
        $nextImage->labelImage("Label $count");
        $imagick->addImage($nextImage);
    }

    $montage = $imagick->montageImage(
        $draw,
        "3x2+0+0", //tile_geometry
        "200x160+3+3>", //thumbnail_geometry
        $montageType, //\Imagick::MONTAGEMODE_CONCATENATE,
        "10x10+2+2"
    );
    
    $montage->setImageFormat('png');
    
    header("Content-Type: image/png");
    echo $montage->getImageBlob();
}