令人困惑的是，get_the_category() 返回类别数组，因此需要循环遍历它们。

这听起来像是您想要分配给当前帖子的类别，也是类别id 11的子类别。如果是这样，请使用

<?php
// Get all the categories assigned to this post
$categories = get_the_category();
// Loop through the array that was returned
foreach($categories as $category) {
    // If this category is a sub-category of category 11
    if($category->parent == 11) {
        // Set the $parent to it
        $parent = $category;
        // And exit the foreach loop
        break;
    }
}
?>