<script>
var $pswp2 = $('.pswp')[0];
      $('.gallery-section').each(function() {
        var $pic2     = $(this),
        getItems2 = function() {
          var items2 = [];
          $pic2.find('a.gallery-popup').each(function() {
            var $href2   = $(this).attr('href'),
            $size2   = $(this).data('size').split('x'),
            $width2  = $size2[0],
            $height2 = $size2[1];

            var item2 = {
              src : $href2,
              w   : $width2,
              h   : $height2
            };

            items2.push(item2);
          });
          return items2;
        };

        var items2 = getItems2();

        $pic2.find('a.gallery-popup').click( function(event) {
          event.preventDefault();
          var $index2 = $(this).data('index');
          var options2 = {
            index: $index2,
            bgOpacity: 0.7,
            showHideOpacity: true
          };

              // Initialize PhotoSwipe
              var lightBox2 = new PhotoSwipe($pswp2, PhotoSwipeUI_Default, items2, options2);
              lightBox2.init();
            });
      });
</script>

<div class="gallery-section">
      <?php
          $galleries = get_field('gallery_images');
          $imgfirst = wp_get_attachment_image_src( $galleries['images'][0], 'full' );
          $full_image_sizes = $imgfirst[1].'x'.$imgfirst[2];
      ?>
      <a href="<?php echo $imgfirst[0]; ?>" data-src="<?php echo $imgfirst[0]; ?>" data-size="<?php echo $full_image_sizes; ?>" data-index="0" class="gallery-popup">
        <img class="full-gallery" src="<?php echo $imgfirst[0] ?>">
      </a>
</div>