Open lightbox via PHP code

I am using Ajax Load More to retrieve images, How could I use lightbox when images are clicked? Help is appreciated. Thanks!

<div class="alm-gallery-img">
   <a href="https://projectdmc.org/support/topic/open-lightbox-via-php-code-2/<?php echo $image ?>" target="_blank" class="popup">
      <img src="<?php echo $image?>"/ data-lazy="true" style="" class="loaded">
   </a>
</div>