How to get attachment caption (get_the_excerpt gives parent post excerpt) ?

I am displaying the attachments on the parent post page with this code :

        $args = array('post_type' => 'attachment', 'post_mime_type' => 'image', 'order'=> 'ASC', 'numberposts' => -1, 'post_status' => null, 'post_parent' => $post->ID ); 
        $attachments = get_posts($args);
        if ($attachments) {
            foreach ( $attachments as $attachment ) {
            $attachments_url[] = $my_image;
            $attachments_caption[] = get_the_excerpt();
            }
        }

problem is that the excerpt doesn’t get the attachment’s caption but the post excerpt.

do you know how to display the attachment’s captions ?
thank you

get_the_excerpt() should work for getting caption just fine.

Your issue is that it looks for post to process in global variables and in your code there you are not setting it up with attachments you are iterating through.

You need to use setup_postdata() for it to work.

Other way would be something like:

get_post_field('post_excerpt', $attachment->ID);