Get current_parent_category in a loop or Cat ancestor- big problem

Question

Im having some trouble since a week now . .. I'm having a bad time with that !

I explain my situation:

I have setup a style for post category.

(a background-color and a small image background).

eg.

Parent A -Child 1 -Child 2 -Child 3

Parent B -Child 1 -Child 2

Parent C -Child 1 -Child 2

The loop i am using is:

<a href="#" class="<?php $category = get_category($cat);
echo $category->category_nicename;?>"><?php single_cat_title('') ?></a> 

This works fine when I'm on a parent_category page, it bring the style I have set up by css, using the category_slug as a class.

(eg of css for on category:)

article.category-business-and-finance .meta-category2 a.business-and-finance {
color: white;
float: left;
padding: 2px;
padding-left: 25px;
background: url(myimg) no-repeat left  ;
background-size: 15px 15px;
background-color: #c3bc19  ;
background-position-x: 5px;
padding-right: 5px;
}

Howver, when I go to the category_page of a child_category, it show up the style of a different category. as some post are set up to multipel parent_category and multiple chld-category as the same time. I don want to create a css for each child_category, as lot of sub category would be added in the futur.

That I d like to achieve, is for the child_category, to bring the class of it's current parent_category slug.

How is this possible to achieve ?

I've tried this loop instead:

<a href="#" class="<?php $parentscategory ="";
foreach((get_the_category()) as $category) {
    if ($category->category_parent == 0) {
        $parentscategory .= ' ' . $category->slug . ' ';
    }
}
echo substr($parentscategory,0,-2);?>"><?php single_cat_title('') ?></a> 

This add the class from all the parent_category attach to the post . .. Is there any way to make it only to the current one ?

( eg. im on the category page of Child-1 from Parent A, but the post is also attach in Parent B and Parent C. it bring me the class of Parent A B and C and the moment - I would like to attach the class of only Parent A - as im on child category of Parent A page).

How can i make this ? should i try a current_parent_category ? cat_ancestor ?

Thank you for all your time,

Answer 1

You could use get_ancestors(). You can transform this:

<a href="#" class="<?php $category = get_category($cat);
echo $category->category_nicename;?>"><?php single_cat_title('') ?></a> 

Into this (I don't know what $cat is as you have not shown it in your question, I assume it is a category ID, if not, you have to provide category ID):

<?php

$cat_ancestors = get_ancestors( $cat, 'category' );
$top_parent = get_category( end( $cat_ancestors ) );

?>

<a href="#" class="<?php esc_attr_e( $top_parent->slug );?>"><?php echo $top_parent->name; ?></a> 

To make the code works also if the category is already the top parent category, you need to check the value returned by get_ancestors. For example:

<?php

$cat_ancestors = get_ancestors( $cat, 'category' );

if( !empty($cat_ancestors) ) {

    $cat = get_category( end( $cat_ancestors ) );

} else {

    $cat = get_category( $cat );

}

?>

<a href="#" class="<?php esc_attr_e( $cat->slug );?>"><?php echo $cat->name; ?></a>