Workaround to walk function no more compatible with Walker in WordPress 5.3

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With te latest releases of WordPress, after updating to WP 5.3 it’s common to receive this error on some custom themes:

Warning: Declaration of _Nav_Menu::walk($elements, $max_depth) should be compatible with Walker::walk($elements, $max_depth, …$args) in…

This is caused by the introduction of the spread operator, as per official WordPress release note:

In WordPress 5.3, the PHP 5.6 spread operator has been introduced to WordPress in a number of places.

Using the spread operator allowed for simplifying the code and improves performance – both in speed as well as memory use -, especially as it has been introduced in a number of functions which are used a multitude of times during every single pageload, such as current_user_can() and add_query_arg().

Most plugins and themes should see no impact of these patches, other than the improved performance.

However, if your plugin/theme is impacted, you will need to take action.

In the file function.php we can use a workaround to adapt the Walk function and change it from:

function walk ($items, $depth) {

                    $this->elements = $this->get_number_of_root_elements($items);

                    return parent::walk($items, $depth);

                }

To:

function walk ($items, $depth,...$args) {

                    $this->elements = $this->get_number_of_root_elements($items);

                    return parent::walk($items, $depth,...$args);

                }

Hope this helps someone with the same problem, feel free to comment below!

Roberto