Remove child categories from Wordpress permalink

functions.php

/*
Remove child categories from Wordpress permalink (https://example.com/%category%/%postname%/ custom structure)

https://example.com/category/sub-category/post-name to https://example.com/category/post-name
*/

function remove_child_categories_from_permalinks( $category ) {
    while ( $category->parent ) {
        $category = get_term( $category->parent, 'category' );
    }
    return $category;
}
add_filter( 'post_link_category', 'remove_child_categories_from_permalinks' );