Get custom category image from menu

Question

I've got myself into a little pickle, and while I'm so close, my understanding of PHP is letting me down.

I want to display the image associated with each category in the menu - working from the answer over here I needed to make that code work with a custom taxonomy as I'm working with woocommerce product categories. I should add that my use case is fairly narrow, so I stripped much of the original answer away to focus on this product category image.

First I add all this to the menu.

<?php add_filter('wp_nav_menu_args', 'add_filter_to_menus');
function add_filter_to_menus($args) {
    add_filter( 'wp_setup_nav_menu_item', 'filter_menu_items' );
    return $args;
} ?>

The next bit is the problematic stuff...

<?php
function filter_menu_items($item) {
    // if the menu item is taxonomy
    if( $item->type == 'taxonomy') {

        // explicitly set the category for now
        $cat_base = 'product-category';

        // strip away everything except the term path
        $cat_path = str_replace(home_url().'/'.$cat_base.'/', '', $item->url);

        // get the term object by using the slug
        $term = get_term_by('slug', $cat_path, 'product_cat');

        // get the term id from the object
        $term_id = $term->term_id;

        // $term_array = get_object_vars($term);
        // echo '<pre>'; var_dump( $term ); echo '</pre>';

        $thumbnail_id = get_woocommerce_term_meta( $term_id, 'thumbnail_id', false );
        $image = wp_get_attachment_url( $thumbnail_id );
        if( !empty($image) ) {
            $item->title =  $item->title . '<span class="menu-image"><img src="' . $image . '" alt=""></span>';
        }
    }
} ?>

Im having a problem getting the $term_id from the $term object. I get a notice Trying to get property of non-object. But when I do a var_dump on $term i get the following:

<pre>object(stdClass)#4511 (10) {
  ["term_id"]=>
  int(21)
  ["name"]=>
  string(9) "Furniture"
  ["slug"]=>
  string(9) "furniture"
  ["term_group"]=>
  int(0)
  ["term_taxonomy_id"]=>
  int(21)
  ["taxonomy"]=>
  string(11) "product_cat"
  ["description"]=>
  string(0) ""
  ["parent"]=>
  int(0)
  ["count"]=>
  int(0)
  ["filter"]=>
  string(3) "raw"
}
</pre>

This looks to me like $term is an object, so why the non-object notice and a total failure? You can also see commented out that I tried to turn this object into an array, but that didn't work out so well either...

Apologies for my PHP skills here - I'm clearly not understanding something fairly basic, but I really did want to solve this myself, but I must admit defeat!

Many thanks for reading.

---

EDIT:

As alluded to in Mark's answer below, the default get_term_by() returns an object. Quite why my code was getting caught up on the is-it-or-isnt-it-an-object thing, I don't know. Using $term = get_term_by('slug', $cat_path, 'product_cat', ARRAY_A); did the trick though, along with using array rather than object syntax to select the value I wanted.

As an aside, I realised that the above would return false if these product categories were nested, as there would be two (or more) slugs being returned; so I did a bit more cleaning up of the slug before attempting to get the term id from it.

Replacing:

$cat_path = str_replace(home_url().'/'.$cat_base.'/', '', $item->url);

With:

$path = parse_url($item->url, PHP_URL_PATH);
$path_trimmed = trim($path, '/');
$parts = explode('/', $path_trimmed);
$cat_path = end($parts);

Answer 1

Not sure why your object is returning the non-object notice, but you can set the output of get_term_by to OBJECT, ARRAY_A, or ARRAY_N - You'll want to use ARRAY_A and then access the term ID via $term['term_id'].

Answer 2

I think this will work for you:

function wpa_category_nav_class( $classes, $item ){
    if( 'product_cat' == $item->object ){
        $classes[] = 'menu-category-' . $item->object_id;
    }
    return $classes;
}
add_filter( 'nav_menu_css_class', 'wpa_category_nav_class', 10, 2 );