Wordpress can't get image url but both the attachment and the actual file are there

Question

The following applies to all attchment images on my site:

There is a PNG image attachment, its ID is 519271.

wp_get_attachment_image(519271, 'thumbnail', false, array( 'id' => 'esjb-preview-image' )) returns "".

wp_get_attachment_image_src(519271) returns false.

wp_attachment_is_image(519271) returns true

The file is there in the uploads folder. Folder permissions are 755. File permissions are 644.

The attachment is in the wp_posts table and the data seems to be OK.

The file has a proper thumbnail in the media library, but when I click on it and it opens the attachment details (/wp-admin/upload.php?item=519271), there's no image there, just the default empty image icon. The details are correct though, including the actual file URL.

I tried deactivating all plugins (except the Really Simple SSL) to no effect.

I re-generated thumbnails using the Regenerate Thumbnails plugin, but the problem still exists.

The site has been hacked recently (WPCoreSys (Dolly) Hack), after which I deleted all files, changed my host password, then uploaded a clean WP, checked my database for any entries that do not belong there, so I presume WP core files are unchanged. The only folders I took from the hacked install were the uploads folder and my theme folder, but I made sure there are no corrupted files there. Anyway, I deactivated my current theme for a time and nothing changed.

Any ideas on what could have caused the problem?

Edit.

This is my code that can't get data:

static function get_image() {
        if(isset($_GET['id']) ){
            $img_id = (int) $_GET['id'];
            $data = array(
                'image' => wp_get_attachment_image($img_id, 'thumbnail', false, array( 'id' => 'esjb-preview-image' ))
            );
            wp_send_json_success( $data );
        } else {
            wp_send_json_error();
        }
    }

The PHP class itself, as well as AJAX request, they both work just fine.

Edit 2.

I cloned my site to a sub-domain, created an empty database and imported images from the main site. I.e. the files are just the same. On the cloned site, the code works just fine and retrieves image data. So it looks like the issue in my database, but the wp_posts tables in both databases look identical to me, their structure is the same, the indices are the same, and there's nothing strange in the data...

Answer 1

Not sure how you're using it, but wp_get_attachment_image_src() returns an array. This should work:

<?php
      $attachmentID = 519271;
      $imageSizeName = "thumbnail";
      $img = wp_get_attachment_image_src($attachmentID, $imageSizeName);
?>

<img src="<?php echo $img[0]; ?>" alt="image">

An alternative to try if it isn't working:

<img src="<?php echo wp_get_attachment_url(519271); ?>" alt="image">

This thread discusses your issue further: wp_get_attachment_image_src always returns false

---

EDIT:

After reading your edit and seeing the site works elsewhere, if it is indeed a corrupted database, try adding this into your wp-config.php file:

define( 'WP_ALLOW_REPAIR', true );

After you have added the line, visit the database repair page: http://your-site.com/wp-admin/maint/repair.php or if you have an SSL certificate, visit https://your-site.com/wp-admin/maint/repair.php.

More information on things that could help found here: https://wpmudev.com/blog/repairing-corrupted-broken-missing-files-databases-wordpress/

Answer 2

Culprit found!

The wp_postmeta table's meta_id field didn't have an auto_increment attribute.

I have no idea why the malware would remove the attribute.

How I found the solution:

I was checking if wp_attachment_is('image') would return true or false for a particular image. It returned false, while get_post_mime_type() returned "image\png". Strange.

I turned to the functions' source code and found out that wp_attachment_is() uses get_attached_file(), which, in turn, retrieves post meta for the attachment, namely the '_wp_attached_file' meta. I then saw that the images that got 'false' from wp_attachment_is('image') had no such meta.

Then I tried to insert a row into the table via PHPMyAdmin. It failed because of the duplicate meta_id of 0. That indicated that meta_id field had no auto_increment attribute.

The rest is simple. I added the attribute and now everything works as a charm.

So, the answer to my question is:

wp_get_attachment_image() returned empty string and wp_get_attachment_image_src() returned false because, while the attachment post was valid, it had no '_wp_attachment_file' meta, therefore WordPress had no data on the file to return. In turn, no meta was added to the attachment post because the 'meta_id' field had no auto_increment attribute, resulting in duplicate entry error every time WordPress tried to add meta to posts. The problem was probably caused by a recent hack.