I was trying to fix some warnings and I noticed that I get constantly

PHP Notice:  Undefined variable:

If I use :

$categories = get_the_category(get_query_var('cat'));
$cat_name = $categories[0]->slug;


$categories = get_category(get_query_var('cat'));
$category_id   = $categories->term_id;
$category_slug = $categories->slug;
$title_page    = $categories->name;

I use it in loops or conditionals


$args1 = array(
  'no_found_rows' => true,
  'update_post_meta_cache' => false,
  'update_post_term_cache' => false,

  'category__in' => array($category_id),
  'posts_per_page' => 2,
  'ignore_sticky_posts' => true,

  'post_type' => 'any'


} else if (has_category($cat_name) && is_single()  && 

I always will get with Debug Mode True, that kind of Warning

So I started to work around it to get some kind of solution, and I noticed that I really didn't understand quite well the difference between get_the_category(); and get_category();

Then I tried :

$cat0 = get_category( get_query_var('cat'));

if(isset($cat0)) {

    $cat1 = get_category(get_query_var('cat'));

    $category_id   = $cat1->term_id;
    $category_slug = $cat1->slug;
    $title_page    = $cat1->name;


$cat4 = get_the_category(get_query_var('cat'));

        $categories = get_the_category(get_query_var('cat'));
        $cat_name = $categories[0]->slug;

    if(isset($cat4) && is_single()){
        $categories = get_the_category(get_query_var('cat'));
        $cat_name = $categories[0]->slug;

but of course if get_category or get_the_category in == NULL

I will get again PHP Notice: Undefined variable: cat_name

What am I missing?

1 Answer 1


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()  && 

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.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.