php - How to make Image Upload Required -

how can section of code made compulsory/required? code doesn't have simple image upload field. joomla component. have tried specifying attribute "required" regular html upload fields, has not worked.

<section class="block" id="gallery">                 <h2><?php echo jtext::_('com_bt_property_gallery');?></h2>                 <div class="center">                     <div class="form-group">                       <?php                     if ($this->params->get('fe_upload_type', 1) == 1) {                         echo $this->loadtemplate('images_flash');                     } else {                         echo $this->loadtemplate('images_simple');                     }                     ?>                     <?php                         $params = new jregistry();                         if ($this->item->params) {                             $params->loadarray($this->item->params);                         }                         $thumb_height = $params->get('thumb_height', $this->params->get("thumb_height", 180));                         $thumb_width = $params->get('thumb_width', $this->params->get("thumb_width", 336));                         if ($thumb_height > 100) {                             $thumb_width = floor($thumb_width * 100 / $thumb_height);                             $thumb_height = 100;                         }                         $thumbimgprocess = $this->params->get('thumbimgprocess', $this->params->get("thumbimgprocess", 1));                         ?>                         <ul id="sortable">                         <?php                             if (is_array($this->images)) {                                  foreach ($this->images $image) {                         ?>                             <li title="double-click make default image"                                 <?php if ($image->default) echo 'class="default_image"' ?>><input class="input-default"                                     <?php if ($image->default) echo 'checked="checked"' ?> title="make default"                                     name="default_image" type="radio" value="<?php echo $image->filename ?>" /> <img                                 class="img-thumb"                                 src="<?php echo juri::root() . $path . '/' . $this->item->id . '/' . ($this->params->get('thumbimgprocess', 1) == -1 ? 'original' : 'thumb') . '-' . $image->filename; ?>" />                                 <input type="hidden" name="image_id[]" value="<?php echo $image->id ?>" /> <?php if ($image->youembed != '') {                                                     ?>                                  <img class="img_video" src="../components/com_bt_property/assets/img/video.png" /> <?php                                             }                                             ?>                                 <input type="hidden" name="image_filename[]" value="<?php echo $image->filename ?>" /> <br />                                 <a href="javascript:void(0)" class="edit" onclick="editimage(this)"><?php echo jtext::_('com_bt_property_edit');?></a> <a                                 href="javascript:void(0)" class="remove" onclick="removeimage(this)"><?php echo jtext::_('com_bt_property_remove');?></a>                             </li>                             <?php                                 }                                 ?>                             <input type="hidden" id="property-hidden" name="video" value="<?php echo htmlspecialchars(json_encode($this->images)); ?>" />                         <?php                             }                             ?>                          </ul>                         <a href="#" class="button" onclick="return removeall()"><?php echo jtext::_('com_bt_property_clear_all');?></a>                     </div>                 </div>                 <p style = "color:red;">             "note: files must not contain form of contact details; names, phone no, email, address, company, website , on. designs such content not approved posting"             </p>             </section> 

i found source code simple image upload button linked above code. had specify required usual, before closing (>) file input tag.