<?php
$imagenes = array('foto1.jpg', 'foto2.jpg');
$i = 0;
$img_canvas = Image::canvas(1800, 1800);
foreach($imagenes as $img) {
    if($img) {
        $path = public_path($img);
        switch($i) {
            case 0:
                $img_canvas->insert($path, 'left');
                break;
            case 1:
                $img_canvas->insert($path, 'right');
                break;
        }
    }
    $i++;
}
$img_canvas->save(public_path('image_merged.jpg'), 100);
$img = Image::make(public_path('image_merged.jpg'));
$img->resize(900, null, function ($constraint) {
    $constraint->aspectRatio();
})->save(public_path('image_merged.jpg'), 100);