<div class="header">
<div class="logo">
    <a href="index.php"><img src="images/logo.jpg" alt="logo" /></a>
</div><!--logo ends-->
<div class="navigation">
    <?php

        $cat_sql = "SELECT * FROM category";
        $cat_query = $conn->query($cat_sql);
        while ($cat_results = $cat_query->fetch_array()){
        $category_page = "category.php?categoryID=" .$cat_results['categoryID'];
            session_start();
            echo session_id();
            echo "<a href='$category_page'>". $cat_results['name'] ." </a>";
        }
    CloseCon($conn)
    ?>
        <a href="admin.php">Admin</a>
</div><!--navigation ends-->
</div><!-- Header ends here-->

$servername = "localhost";
$username = "root";
$password = "123456789";
$database = "accessories";

$conn = new mysqli($servername, $username, $password, $database);

if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";a

function CloseCon($conn)
{$conn -> close();}