<?php
 $query=mysqli_query($db,"select id_fotografia, foto, id_album from fotografias order by id_fotografia DESC limit 10");
 while($cat=mysqli_fetch_assoc($query)){?>
   <div class="col-md-6">
      <div class="portfolio-item">
        <a data-toggle="modal" data-target="#myModal" data-id="<?php echo $cat['id_fotografia']; ?>">
             <img class="img-portfolio img-responsive" src="<?php echo $cat['foto']; ?>">
         </a>
       </div>
     </div>
<?php } ?>

<div id="myModal" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true"
    <div class="modal-dialog">
       <div class="modal-content">
           <div class="modal-body">
            <img src="//want the same photo appears here" class="img-responsive">
            </div>
        </div>
    </div>
</div>