When you have the large collection of images files in a directory and you want to convert it into the photo gallery.

Solution 1
Add image file manually to your page one by one which you want to show. The problem with this solution is it is time-consuming and you have to check all image links if any update in future.

Solution 2
Store image names in the Database table and use it to get images.

Solution 3
Read all files from target directory and generate photo gallery.
The second and third solution is better but in this post, I will only show you how to implement the third solution with PHP.

1. Download and Include

• I am using simplelightbox jQuery library for making the gallery which you can download it from here.
• Include simplelightbox.min.css and simple-lightbox.js.

<link href='simplelightbox-master/dist/simplelightbox.min.css' rel='stylesheet' type='text/css'>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>
<script type="text/javascript" src="simplelightbox-master/dist/simple-lightbox.js"></script>

2. HTML and PHP

Reading files from a directory with PHP.

• I am reading files from images directory which also have sub-directory thumbnail.
• The directory and file structure looks like this –

---

Specified valid image extensions in the  $image_extensions Array variable and target directory in $dir.
Read all files from the directory and set thumbnail and image path.
If it is a valid image and not a directory then uses the path in the image source.
I only use $count variable to show 4 images in a row.
Completed Code

<div class='container'>
 <div class="gallery">
 
  <?php 
  // Image extensions
  $image_extensions = array("png","jpg","jpeg","gif");

  // Target directory
  $dir = 'images/';
  if (is_dir($dir)){
 
   if ($dh = opendir($dir)){
    $count = 1;

    // Read files
    while (($file = readdir($dh)) !== false){

     if($file != '' && $file != '.' && $file != '..'){
 
      // Thumbnail image path
      $thumbnail_path = "images/thumbnail/".$file;

      // Image path
      $image_path = "images/".$file;
 
      $thumbnail_ext = pathinfo($thumbnail_path, PATHINFO_EXTENSION);
      $image_ext = pathinfo($image_path, PATHINFO_EXTENSION);

      // Check its not folder and it is image file
      if(!is_dir($image_path) && 
         in_array($thumbnail_ext,$image_extensions) && 
         in_array($image_ext,$image_extensions)){
   ?>

       <!-- Image -->
       <a href="<?php echo $image_path; ?>">
        <img src="<?php echo $thumbnail_path; ?>" alt="" title=""/>
       </a>
       <!-- --- -->
       <?php

       // Break
       if( $count%4 == 0){
       ?>
         <div class="clear"></div>
       <?php 
       }
       $count++;
      }
     }
 
    }
    closedir($dh);
   }
  }
 ?>
 </div>
</div>

3. CSS

.container .gallery a img {
  float: left;
  width: 20%;
  height: auto;
  border: 2px solid #fff;
  -webkit-transition: -webkit-transform .15s ease;
  -moz-transition: -moz-transform .15s ease;
  -o-transition: -o-transform .15s ease;
  -ms-transition: -ms-transform .15s ease;
  transition: transform .15s ease;
  position: relative;
}

.container .gallery a:hover img {
  -webkit-transform: scale(1.05);
  -moz-transform: scale(1.05);
  -o-transform: scale(1.05);
  -ms-transform: scale(1.05);
  transform: scale(1.05);
  z-index: 5;
}

.clear {
  clear: both;
  float: none;
  width: 100%;
}

4. jQuery

Initialize simpleLightbox by calling simpleLightbox() method on <a> of gallery class.

<!-- Script -->
<script type='text/javascript'>
$(document).ready(function(){

 // Intialize gallery
 var gallery = $('.gallery a').simpleLightbox();

});
</script>

5. Conclusion

You have only need to specify your target directory where you have stored your images if any file found other then image then the PHP script skip it.
You can use any other jQuery library for the photo gallery and adjust the layout.
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