get_posts ignoring 'category' and displaying all posts

Question

I'm going a bit crazy on this one. I'm trying to display a list of posts in a category on an Admin page in a plugin I am writing. The following code works fine on my dev server (OS X/Apache):

$args = array(
    'posts_per_page' => $pageSize,
    'offset'=> $offset,
    'category' => 9
);

$posts = get_posts($args);

foreach ($posts as $key => $aPost) {
    (...)
}

As you might suspect, I get only posts in the category with an ID of 9. Now, on my production server (Linux/Nginx) it shows all posts - as if the category argument was never set. I only mention the nginx/apache/linux/os x as everything else is running the same - same themes and plugins installed (with the exception of Jetpack on the production server).

Any thoughts?

Answer 1

Ok. After a frustrating weekend I have a workaround (but still not real reason why the simpler version worked on one install and not another!)

$args = array(
    'posts_per_page' => $pageSize,
    'offset'=> $offset,
    'tax_query' => array(
        array(
            'taxonomy' => 'category', 
            'field' => 'term_id', 
            'terms' => 9
        )
);

While this is a totally workable solution, I'm still baffled.