How to fix PHP errors

There is a lot of PHP warning in the server error.log file like this:

PHP Warning:  Attempt to read property “ID” on null in …/wp-content/plugins/woocommerce-unit-of-measure/public/class-wc-uom-public.php on line 86

Since this plugin developer hasn’t fix this in months, I desided to give it a try. Here is how can you do it:

1. Open the /public/class-wc-uom-public.php
2. Find the line 83 where is like this: private function woo_uom_output_getter($uom_item_id = null) {
3. After that line you need to change some lines.

Old code:

private function woo_uom_output_getter($uom_item_id = null) {
if (is_null($uom_item_id)) {
global $post;
$uom_item_id = $post->ID;

And you need to change into this:

        private function woo_uom_output_getter($uom_item_id = null) {
            if (is_null($uom_item_id)) {

            // global $post;

            // $uom_item_id = $post->ID;

            global $post, $product;

            // 1) If there is global $product

            if (isset($product) && is_a($product, 'WC_Product')) {

                $uom_item_id = $product->get_id();

                // 2) If there is $post

            } elseif (isset($post) && is_object($post) && isset($post->ID)) {

                $uom_item_id = (int) $post->ID;

                // 3) Queried object ID (single product page)

            } else {

                $queried_id = get_queried_object_id();

                if ($queried_id) {

                    $uom_item_id = (int) $queried_id;

                }

            }

        }

        if (empty($uom_item_id)) {

            return '';

        }

This is fix the code and error messages are gone. Plugin works as expected.