OOP: display result of a database with while loop

Hi,
I am very new to OOP in PHP, I have mysite running with the conventional procedure, such as displaying my site menu in this way in a php file, menu.php

<?php
$sql = "
SELECT *
FROM menu
ORDER BY order ASC";

$result = mysql_query($sql);
?>

<ul>
	<?php 
	while($row = mysql_fetch_assoc($result))
	{ 
	?>
	<li><a href="<?php echo $row['link'];?>"><?php echo $row['name'];?></a></li>
    <?php
	}
	?>
</ul>

now I would like to practise it in OOP, so I would like to separate PHP core code and html, class_lib.php, and menu.php

this is what I would put in class_lib.php,

$mysqli= new MySQLi('localhost', 'root', 'xxx', 'my_db');

Class menu
{

public function get_menu()
	{

	$mysqli = new mysqli();

	$sql = "
	SELECT *
	FROM menu
	ORDER BY order ASC";

	$result = $mysqli->query($sql);
	}

}

so in my menu.php, I would just want to instantiate the menu object, and pulling data from the menu class,

<ul>
	<?php 
        $menu = new menu();
	$menu->get_menu();
	while($row = $menu->fetch_assoc())
	{ 
	?>
	<li><a href="<?php echo $row['link'];?>"><?php echo $row['name'];?></a></li>
    <?php
	}
	?>
</ul>

but i won’t get anything, I think probably my idea is incorrect??

will be grateful if u know how to correct this.

many thanks,
Lau