I have a navigation menu in Wordpress. I would like it to check if the page has a custom field of "menu_icon" and if it does, add that custom field into the menu item it corresponds to. I'm sure this would require some sort of walker function extension but I am a bit new to PHP and Wordpress. I've search around and have not found a suitable tutorial.
For example: (normal menu)
<ul> <li><a href="#">link</a></li> </ul> (custom) <ul> <li><span class="icon" style="background-image:url(CUSTOM FIELD CALLED HERE);"></span><a href="link">link</a></li> </ul>