Fix Warnings that shouldn't be necessary to fix

So there’s two things going on here. Firstly get_the_category() doesn’t accept a category ID as a parameter. It accepts a post ID for which to get categories from.

Judging by your code you need to use get_category():

$category = get_category( get_query_var('cat') );

The other problem is that you seem to be using $cat_name without checking if you actually have a category.

For example:

$category = get_category( $nonexistant_cat_id );

if ($category) {
    $cat_name = $category->slug;
}

echo $cat_name; // Will be an undefined variable;

In that example $cat_name isn’t being set, because get_category() didn’t return a category. So you can only use $cat_name if get_category() returned a category:

$category = get_the_category( $nonexistant_cat_id );

if ($category) {
    $cat_name = $category->slug;
    echo $cat_name; // No longer undefined variable;
}

Or in your example, just check if $cat_name is set in the condition before using $cat_name:

} else if (isset($cat_name) && has_category($cat_name) && is_single()  && 
!is_singular('my_post_type')){

The characterisation of this being an error that “shouldn’t be necessary” to fix is incorrect. There are several problems in your code you need to address.

Related Posts: