WordPress ACF: Image field, change image on mouse over

Instead of this:

 <?php $image = wp_get_attachment_image_src(get_sub_field('med_foto'), 'medium'); ?>
 <?php $thumb = wp_get_attachment_image_src(get_sub_field('med_foto'), 'thumbnail'); ?>
 <img src="<?php echo $image[0]; ?>" alt="<?php  the_sub_field('med_naam');?>" rel="<?php echo $thumb[0]; ?>" />

I use this (and its working):

  <?php $image = wp_get_attachment_image_src(get_sub_field('med_foto'), 'medium'); ?>
  <?php $image2 = wp_get_attachment_image_src(get_sub_field('med_foto2'), 'medium'); ?>
  <?php $thumb = wp_get_attachment_image_src(get_sub_field('med_foto'), 'thumbnail'); ?>
  <img src="<?php echo $image[0]; ?>" alt="<?php  the_sub_field('med_naam');?>"
  rel="<?php echo $thumb[0]; ?>" onmouseover="this.src='<?php echo $image2[0]; ?>'" 
  onmouseout="this.src='<?php echo $image[0]; ?>'" />

Original Question:

I have a flexible content field containing a name, a link to a personal page and 2 image fields (both returning object id): the original image and a “mouse-over” image.

I want to display these fields on a page, so i added the following code (between a while-statement, but that messes up the code:

<?php if(get_row_layout() == "medewerker"): // layout: Content ?>
        <div class="medewerker_blok">
            <div class="med_naam">
                <?php the_sub_field("med_naam"); ?>
            </div>
            <a href="<?php the_sub_field('medewerkers_pagina'); ?>" > 
            <div class="med_foto">
                <?php $image = wp_get_attachment_image_src(get_sub_field('med_foto'), 'medium'); ?>
                <?php $thumb = wp_get_attachment_image_src(get_sub_field('med_foto'), 'thumbnail'); ?>
                <img src="<?php echo $image[0]; ?>" alt="<?php  the_sub_field('med_naam');?>" rel="<?php echo $thumb[0]; ?>" />

            </div>
            </a>
        </div>
        <div class="clear"></div>

<?php endif; ?>

This works fine: it shows the name field, the image.
So far so good.
But now I would like an option where it replaces this image with the second image field when you hover over the picture.

I cant get it working, must be missing something.

Please note, it is a flexible field, so the mouseover shouldn’t trigger al the other repeated blocks.

I hope someone can help me with this!

Cheers,

Bram