gistfile1.txt

$slugs = array('overview', 'advertising', 'bacon');

foreach ($slugs as $slug) {
		$ids = get_posts( array(
        'post_type' => 'attachment',
        'post_status' => 'any',
        'posts_per_page' => -1,
        'tax_query' => array(
            array(
                'taxonomy' => 'media_category',
                'field' => 'slug',
                'terms' => array($slug),
            ),
        ),
	      'fields' => 'ids', // only return IDs
	  ));
    echo "SLUG" . $term_slug; echo "IDs"; var_dump($ids);
}

//first var_dump() always returns empty, even when slug doesn't change