wp_get_attachment_image() not displaying post images even though wp_get_attachment_url() echo correct urls

Question

I am trying to make a widget which takes post id as input from user and displays images of the specified post in sidebar. wp_get_attachment_url() gets me the url but in the next line wp_get_attachment_image() doesn't display image on same photo=>id. I don't know where I am going wrong. I am confirming urls from the post content because otherwise wp_get_attachment_image() was returning all of the media libary. But now wp_get_attachment_image() no longer working.

Sharing the code of the widget I am tried to put together after going through other wordpress support group and stack exchange posts:

function widget( $args, $instance ) {
 echo $args['before_widget'];
 $photos = get_children( array('post_parent' => $instance['post'],  'post_type' => 'attachment', 'post_mime_type' => 'image') );

 //for getting inline post images only
 $post_id=$instance['post'];
 $content_post = get_post($post_id);
 $content = $content_post->post_content;
 $content = apply_filters('the_content', $content);
 $content = str_replace(']]>', ']]>', $content);

 if (!empty($photos)) :
 //Loop through each attachment..

 foreach ($photos as $photo_id => $photo) :
    //getting inline post images only
    $url = wp_get_attachment_url($photo_id);
    $position = strpos($content, $url);

    if($position){
        echo $post_id;
        //working shows all the attached photo urls
        echo wp_get_attachment_url($photo_id);
        //not working
        wp_get_attachment_image($photo_id, 'thumbnail') ;
    }
 endforeach ;
 endif ;

Answer 1

When saying "not working" you should include what you expect and what you get; "not working" says very little about the problem you have. Without knowing what the exact problem you have, I guess you don't see the image. In that case I suggest to change this:

wp_get_attachment_image($photo_id, 'thumbnail');

With:

echo wp_get_attachment_image($photo_id, 'thumbnail');

wp_get_attachment_image() returns the HTML image element, but doesn't print it.