Wordpress 子・孫カテゴリIDを取得

親子間の子カテゴリ取得

$categories = get_the_category();
foreach ( $categories as $category ) {
  if($category->parent){
    $catename = $category->name;
    $childcateid = $category->cat_ID;
  }
}

親子孫間での特定の子カテゴリ取得

$cat = get_the_category();
foreach ( $cat as $category ) {
    $parent = $category->parent;
    if( $parent == ここにID ){
        $catename = $category->name;
        $childcateid = $category->cat_ID;// これもID
        $childcateid = $category->term_id;// これもID
    }
}