Retrieve Image from Media Library by it's category

Question

What I am needing to do here is get an image from the media library only by it's category. It won't be attached to a post, meaning that, the image will not be uploaded as a "featured image" of any post type. It will be uploaded directly through the media library. However I have created a function that will allow me to apply custom categories to those images. I have been successful at pulling images from my media library with the following:

$query_images_args = array(
'post_type' => 'attachment',
'post_mime_type' =>'image',
'post_status' => 'inherit',
'posts_per_page' => -1,
);

$query_images = new WP_Query( $query_images_args );
$images = array();
foreach ( $query_images->posts as $image) {
    $images[]= wp_get_attachment_url( $image->ID );
}

And this is my custom function for categories:

function add_attachment_taxonomy() {
$labels = array(
    'name'              => 'Categories',
    'singular_name'     => 'Category',
    'search_items'      => 'Search Category',
    'all_items'         => 'All Category',
    'parent_item'       => 'Parent Category',
    'parent_item_colon' => 'Parent Category:',
    'edit_item'         => 'Edit Category',
    'update_item'       => 'Update Category',
    'add_new_item'      => 'Add New Category',
    'new_item_name'     => 'New Category Name',
    'menu_name'         => 'Categories',
);

$args = array(
    'labels' => $labels,
    'hierarchical' => true,
    'query_var' => 'true',
    'rewrite' => 'true',
    'show_admin_column' => 'true',
);

register_taxonomy( 'attachment_category', 'attachment', $args );
}
add_action( 'init', 'add_attachment_taxonomy' );

However when I add 'category_name' => term_slug it continues to show nothing. Is there something else I need to be doing to make this work?

Answer 1

'category_name' will not work. You are making use of a custom taxonomy, not build-in categories. It seems from this that you have a misunderstanding about taxonomies. Please take your time and see this post on this particular subject

For custom taxonomies, use a tax_query to retrieve the posts that you need. Here is an example:

$query_images_args = array(
    'post_type' => 'attachment',
    'post_mime_type' =>'image',
    'post_status' => 'inherit',
    'posts_per_page' => -1,
    'tax_query' => array(
        array(
            'taxonomy' => 'attachment_category',
            'field'    => 'slug',
            'terms'    => 'SLUG OF YOUR TERM',
        ),
    ),
);
$query_images = new WP_Query( $query_images_args );