Call custom field into menu item

Question

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>

Answer 1

This is what i have used for checking to see if the custom field is there or not. I am sure you can use it as well.

<?php 
    $custom_field = get_post_meta($post->ID, 'Your Custom Field Name', true);

    // Checks to see if there is a value in the custom field
    if($custom_field != '') { echo $custom_field; }
?>

It probably would look something like this with your code above:

<ul>
   <li><span class="icon" style="background-image:url(<?php 
    $custom_field = get_post_meta($post->ID, 'Your Custom Field Name', true);

    // Checks to see if there is a value in the custom field
    if($custom_field != '') { echo $custom_field; }
?>);">   </span><a href="link">link</a></li>
</ul>

Answer 2

You can use the get_post_meta function:

<?php 
$value = get_post_meta($post->ID, 'CUSTOM_FIELD_NAME', true);

if($value != '') {
  echo $value;
} 
?>

Read more about it here: http://codex.wordpress.org/Function_Reference/get_post_meta