<script src="https://code.jquery.com/jquery-2.2.4.min.js" integrity="sha256-BbhdlvQf/xTY9gja0Dq3HiwQF8LaCRTXxZKRutelT44=" crossorigin="anonymous"></script>
<script>
$(document).on("click",".file",function(){
  item_url = $(this).data("src");
  var args = top.tinymce.activeEditor.windowManager.getParams();
  win = (args.window);
  input = (args.input);
  win.document.getElementById(input).value = item_url;
  top.tinymce.activeEditor.windowManager.close();
});
</script>
<?php
$path = 'cupload/images/'; // this is the image folder
$files = GLOB($path.'*{.jpg,.png}',GLOB_BRACE);
if (!EMPTY($files)) {
    echo '<ul style="display: inline-block; width: 100%; box-sizing: border-box; list-style: none; padding: 0;">';
    foreach ($files as $file) {
        $file_name = basename($file);
        $file = str_replace(' ', '%20', $file);
        echo "<li class='file' data-src='".$path.$file_name."' style='margin: 10px; width: 100px; display: inline-block; height: 100px; float: left; cursor: pointer;'>
            <div class='file_image' title='".$file_name."' style='display: block; width: 100px; height: 100px; background-image: url(/".$path.'thumb/'.$file_name."); background-position: center center; background-size: cover;'></div></li>";
    }
    echo '</ul>';
}
?>