Query child's child categories

Question

I'm building a query to get the child's child categories. For example : I have a parent category named 'animal' and others like 'food' and 'sport'. I want to get animal's sub categories.

I do :

$parent_cat = get_cat_ID( $cat_name );
$args = array(
    'type'      => 'post',
    'parent'    => $parent_cat,
    'order'     => 'DESC'
);
$categories = (array) get_categories( $args );

And no problem, with a foreach I get my animal's sub categories.

In my sub categories, I also have categories (this is a 3 levels hierarchy).

I do the same :

$child_cat = get_cat_ID( $sub_cat_name );
$args = array(
    'type'      => 'post',
    'parent'    => $child_cat,
    'order'     => 'DESC'
);
$sub_categories = (array) get_categories( $args );

And... it returns the others parents categories 'food' an 'sport'.

Why that ? Where am I wrong ?

Answer 1

Ok then, I actually was getting the subcats with the wrong method.

in $parent_cat = get_cat_ID( $cat_name ); $cat_name wasn't a name but un slug. First mistake.

So I corrected with $parent_cat = get_category_by_slug( $cat_slug );

The final code is :

// Get the parent cat thanks to the page's cat slug
$parent_cat = get_category_by_slug( $cat[1] );
$args = array(
    'type'      => 'post',
    'parent'    => $parent_cat->term_id,
    'order'     => 'DESC'
);
// child cats
$categories = get_categories( $args );
// loop on the child cats to get the sub cats object
foreach ($categories as $key => $value) {
    return $value;
}

That's it.