How to display images that was uploaded in the media gallery and not by the current post?

Question

I have uploaded images before in my other posts and now I want to display it in my Photo Gallery. I'm using an isotope layout so I'm not using the native gallery of WordPress. It's working just fine however I can't display the images that is not uploaded directly to that post. For example the images that I've uploaded before. If I upload a new one to this current post, then that will display.

Here's my code:

        // DISPLAY ALL IMAGES FROM A PARENT GALLERY
        $attachments = get_children(array('post_parent' => $post->ID,
          'post_status' => 'inherit',
          'post_type' => 'attachment',
          'post_mime_type' => 'image',
          'order' => 'ASC',
          'orderby' => 'menu_order ID'));
        foreach($attachments as $att_id => $attachment) {

So how can I display those past images in my gallery?

Answer 1

Changing 'post_parent' => $post->ID to 'post_parent' => null will fetch all images.