Title: [Plugin: Thumbnails for Backend] Function not defined
Last modified: August 20, 2016

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# [Plugin: Thumbnails for Backend] Function not defined

 *  Resolved [mirer03](https://wordpress.org/support/users/mirer03/)
 * (@mirer03)
 * [14 years, 6 months ago](https://wordpress.org/support/topic/plugin-thumbnails-for-backend-function-not-defined/)
 * Don’t know what I’m doing wrong … are there some prerequisites I have to fullfill?
   When going to the Articles or pages in the Backend, I only see this in the Box:
 * Fatal error: Call to undefined function get_post_thumbnail_id() in … /wp-content/
   plugins/thumbnailsforbackend/thumbnailsforbackend.php on line 109
 * Which is:
    $id_thumb = get_post_thumbnail_id($post->ID);
 * Where should this function be defined? Is it missing in my template?
 * [http://wordpress.org/extend/plugins/thumbnailsforbackend/](http://wordpress.org/extend/plugins/thumbnailsforbackend/)

Viewing 4 replies - 1 through 4 (of 4 total)

 *  Plugin Author [g100g](https://wordpress.org/support/users/g100g/)
 * (@g100g)
 * [14 years, 6 months ago](https://wordpress.org/support/topic/plugin-thumbnails-for-backend-function-not-defined/#post-2414349)
 * Hi,
    ii fixed this issue with theme don’t add support to Post Thumbnail.
 * You can download update here
    [http://wordpress.org/extend/plugins/thumbnailsforbackend/](http://wordpress.org/extend/plugins/thumbnailsforbackend/)
 * Thanks you for advise.
 *  Thread Starter [mirer03](https://wordpress.org/support/users/mirer03/)
 * (@mirer03)
 * [14 years, 6 months ago](https://wordpress.org/support/topic/plugin-thumbnails-for-backend-function-not-defined/#post-2414360)
 * Wow, now that was quick 🙂 Works for me now – thank you!
    Maybe one minor issue
   is left: In articles where I use an ‘old’ picture which I already used before,
   there is no picture. Is this ‘normal’ or part of the fix for the thems not supporting
   the thumbnails?
 *  Plugin Author [g100g](https://wordpress.org/support/users/g100g/)
 * (@g100g)
 * [14 years, 6 months ago](https://wordpress.org/support/topic/plugin-thumbnails-for-backend-function-not-defined/#post-2414365)
 * Hi,
    the plugin get the thumbnail image from images attached to post. Inside 
   media Library.
 * If the image is inside the post content, but not attached to post gallery, no
   thumbnail will be show.
 * Let me know if is it this the case.
 * Thanks!
 *  Thread Starter [mirer03](https://wordpress.org/support/users/mirer03/)
 * (@mirer03)
 * [14 years, 6 months ago](https://wordpress.org/support/topic/plugin-thumbnails-for-backend-function-not-defined/#post-2414377)
 * Then everything works fine! As I tried to describe, the articles which don’t 
   show a picture use ‘old’ pictures from other articles because our guys don’t 
   take enough new pictures 😉
    Thanks for the nice plugin and quick support!

Viewing 4 replies - 1 through 4 (of 4 total)

The topic ‘[Plugin: Thumbnails for Backend] Function not defined’ is closed to new
replies.

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 * 4 replies
 * 2 participants
 * Last reply from: [mirer03](https://wordpress.org/support/users/mirer03/)
 * Last activity: [14 years, 6 months ago](https://wordpress.org/support/topic/plugin-thumbnails-for-backend-function-not-defined/#post-2414377)
 * Status: resolved