所选文章的页面不显示内容

I have my website LOCATED HERE.

If you click on "FREE" on the home page then click one of the logos for the 2 offers to be diverted to the /single.php?id= page, You can see that the logo and text are displayed.

However MY PROBLEM IS: if you click on "GIFT" from the home page you can see the logo and description but then clicking on the logo it brings up the /single.php?id= page once again but it has a problem loading.

my code for single.php is:

<?php

include_once('include/connection.php');
include_once('include/article.php');

$article = new storearticle;

if(isset($_GET['id'])) {
   $id = $_GET['id'];
$data = $article->fetch_data($id);

?>

<html>

<head>
<title>Xclo Mobi</title>
<link rel="stylesheet" href="other.css" />
</head>

<body>
<?php include_once('header.php'); ?>


<div class="container">
<a href="index.php" id="logo">Title Page</a><br /><br />

<div align="center">
<img src="<?php echo $data['promo_image']; ?>" class="img"><br />

<font class="title"><?php echo $data['promo_title']; ?></font>


<p>
<?php echo $data['promo_content']; ?>


<a href="<?php echo $data['promo_link']; ?>" target="_blank"><img alt="" title="" src="GO.png" height="50" width="50" align="right" /></a>

<br /><br /></div>
<b><u>More From This Brand</b></u>

<br /><br />


<a href="index.php">&larr; Home</a>

</div>
<?php include_once('footer.php'); ?>
</body>

</html>



<?php
} else { 
 header('location: index.php');
 exit();
}

?>

can someone please tell me where I am going wrong because I have been trying to fix this for days.

If you need any more information from me then please ask. thank you.