ACF Plugin - Random Gallery Image with wp_get_attachment_image()

Question

I’ve found others (source 1, source 2, source 3) using the following code for displaying a random gallery image (and it works) with the ACF Plugin:

<?php
$gallery = get_field('images');
$rand = array_rand($gallery, 1);

if( $gallery ): ?>
    <img src="<?php echo $gallery[$rand]['sizes']['large']; ?>" alt="<?php echo $gallery[$rand]['alt']; ?>" />
<?php endif; ?>

But I’m trying to do it with wp_get_attachment_image() (for responsive images) but not sure how to get the $rand variable working? The ACF Documentation for the Gallery field has a 'Basic List of Images" example that uses wp_get_attachment_image() but I'm not needing to loop through the gallery.

Any help would be greatly appreciated. I think it has to be something like the following, with the $rand variable added somewhere:

<?php 
    $images = get_field('gallery');
    $size = 'full'; // (thumbnail, medium, large, full or custom size)
    $rand = array_rand($images, 1);

    if( $images ): ?>
            <?php echo wp_get_attachment_image( $images['ID'], $size ); ?>
<?php endif; ?>

Answer 1

<?php 
    $images = get_field('gallery');
    $size = 'full'; // (thumbnail, medium, large, full or custom size)
    $rand = array_rand($images, 1);

    if( $images ): ?>
            <?php echo wp_get_attachment_image( $images[$rand]['ID'], $size ); ?>
<?php endif; ?>

This code should work. array_rand() return key if second param set to 1 or array with keys if second param > 1

Answer 2

Answer found via ACF Forums. Adding the false parameter returns raw/unformatted value.

<?php 
    $images = get_field('gallery', 'option', false); // Adding the `false` parameter returns raw/unformatted value
    $size = 'full'; // (thumbnail, medium, large, full or custom size)
    $rand = array_rand($images, 1);

    if( $images ): ?>
        <?php echo wp_get_attachment_image( $images[$rand], $size ); ?>
<?php endif; ?>