How do I check If sub category of category x in WordPress?

3 comments

1. Although very old, I’ve created the perfect solution.

   Add this to your functions.php file:

   /** check if the current category is a child of a given category **/
   function current_cat_is_sub_of($parent = ''){
       global $wp_query;
       $cat = $wp_query->get_queried_object();
   
       if ( ! isset( $wp_query ) ) {
           _doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1.0' );
           return false;
       }
       elseif( $cat->parent!=0 && $cat->parent == $parent ){
           return true;
       }
       else{
           return false;
       }
   }
   

   Then you can use it various ways. For example to change the displaying order of posts in all subcategory pages under a given category:

   /** order posts under category 123 from new to old **/
   function order_digital_posts($query){
       if (current_cat_is_sub_of('THE PARENT CATEGORY ID') && $query->is_main_query()) {
           $query->set( 'order', 'ASC' );
       }
   }
   add_action('pre_get_posts', 'order_digital_posts');
   

   Enjoy!
   Itamar

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2. Old question, but I stumbled on this last night and I had to find an answer for myself.

   This is on my category.php page:

   $category = get_the_category();
   
   if(isset($category[1]) && $category[1]->slug === 'catagory-you-want') {
   
       // Do stuff if it's a child of "Category You Want"
       // You can use $category[1]->cat_ID to check which category instead
   
   }
   

   The current subcategory is in $category at position 0.

   This would be harder if “Category You Want” had a parent category and you didn’t know it.

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3. You can see if your current category parent id matches the “blog” category id. If so, your current category is a subcategory of “blog”.

   $current_cat = get_query_var("category");
   $cat = get_term_by('slug',$current_cat,"category");
   $blog = get_term_by('slug',"blog","category");
   
   
   if($cat->parent == $blog->ID){ /*your code */ }
   

   This code will do the functionality you described.

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