Trying to create a multiple grid view Gallery in Wordpress with flexslider

[amitabha197]

I am trying to create multiple grid view gallery with wordpress custom post thumbnail .
My HTML CODE is:

<ul class="slides">
 <li>
    <div class="photo-1">
  <img src="images/photostream/one.jpg" width="101" height="102">
   <span class="flex-photoCaption"><a href=""> <i class="fa fa-search"></i></a></span>
    </div>
     <div class="photo-1">
      <a href=""><img src="images/photostream/two.jpg" width="101" height="102"></a>
      <span class="flex-photoCaption"> <a href=""><i class="fa fa-search"></i></a></span>
       </div>
      <div class="photo-1">
        <a href=""><img src="images/photostream/three.jpg" width="101" height="102"></a>
        <span class="flex-photoCaption"> <a href=""><i class="fa fa-search"></i></a></span>
        </div>
         <div class="photo-1">
         <a href=""><img src="images/photostream/four.jpg" width="101" height="102"></a>
          <span class="flex-photoCaption"> <a href=""><i class="fa fa-search"></i></a></span>
           </div>
            </li>
<li>
    <div class="photo-1">
  <img src="images/photostream/one.jpg" width="101" height="102">
   <span class="flex-photoCaption"><a href=""> <i class="fa fa-search"></i></a></span>
    </div>
     <div class="photo-1">
      <a href=""><img src="images/photostream/two.jpg" width="101" height="102"></a>
      <span class="flex-photoCaption"> <a href=""><i class="fa fa-search"></i></a></span>
       </div>
      <div class="photo-1">
        <a href=""><img src="images/photostream/three.jpg" width="101" height="102"></a>
        <span class="flex-photoCaption"> <a href=""><i class="fa fa-search"></i></a></span>
        </div>
         <div class="photo-1">
         <a href=""><img src="images/photostream/four.jpg" width="101" height="102"></a>
          <span class="flex-photoCaption"> <a href=""><i class="fa fa-search"></i></a></span>
           </div>
            </li>
                                        
        </ul>

For Custom template I am doing

<ul class="slides">
  <?php 
                                    
                                    
 global $post;
$photo_args = array(
                                                      
        'post_type' => 'photo_gallery',
        'posts_per_page' => -1,
                                                       
        'order'  => 'ASC',
        
                                           
        );
                                           
                                         
        $photo_querys = get_posts( $photo_args );
                                         
                                         
        ?>
                                       
  <?php foreach($photo_querys as $post)  : setup_postdata($post); ?>
                                        
                                           
   <li>
                                       
    <?php 
                                        
$element_show = 1;
$element_show  = '<div class="photo-1">'. the_post_thumbnail('gallery_image').'
                 <span class="flex-photoCaption"><a href=" '. get_permalink(). '"> <i class="fa fa-search"></i></a></span>
                     </div>';
                  $element_to_show = 2 * $element_show  ;?>
                                          <?php echo $element_to_show ; ?>
       </li>
                                        
    <?php  endforeach; ?>
<?php wp_reset_postdata();  ?>
</ul> 

Images are showing but there is showing “0” value after the “li” elements
This is from my view source

<li style="width: 120px; float: left; display: block;">
<img draggable="false" src="http://localhost/azadfoundation/final/wp-content/uploads/2014/11/selfdefense8_fs-100x102.jpg" class="attachment-gallery_image wp-post-image" alt="selfdefense8_fs" height="102" width="100">                                          
0
</li>

I am actually trying to do this

But what I am getting is this

I am very sure that I am doing wrong with my code. Can anyone please help me to solve this.
Thanks in advance.