# Critical Error: Call to undefined function mb\_convert\_encoding
**URL:** https://meta.discourse.org/t/critical-error-call-to-undefined-function-mb-convert-encoding/386125
**Category:** WordPress
**Created:** [October 19, 2025, 7:04pm UTC](https://meta.discourse.org/t/critical-error-call-to-undefined-function-mb-convert-encoding/386125 "2025-10-19T19:04:44Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@cogdog](https://meta.discourse.org/u/cogdog)
#### Post date: [October 19, 2025, 7:04pm UTC](https://meta.discourse.org/t/critical-error-call-to-undefined-function-mb-convert-encoding/386125/1 "2025-10-19T19:04:44Z")
I sam trying to get the Discourse Block to display our posts published to discourse. They successfully publish. I added the block in the Site editor, but nothing appears. To expolore, I added the Discourse block to the post. In preview, it showed the “Join the Conversation in Discourse Now” but had no comments (the discourse post has one reply).
I have disabled the plugin for now.
This generated a WordPress critical error (trace pasted below). The info on our server:
```plaintext
WordPress version 6.8.3
Active theme: OEG Main (version 0.1.9)
Current plugin: WP-Discourse (version 2.5.9)
PHP version 8.3.19
```
The trace reported back.
```plaintext
Error Details
=============
An error of type E_ERROR was caused in line 335 of the file
/home/webapps/oeglobal/wp-content/plugins/wp-discourse/lib/template-functions.php.
Error message: Uncaught Error: Call to undefined function
WPDiscourse\Shared\mb_convert_encoding() in
/home/webapps/oeglobal/wp-content/plugins/wp-discourse/lib/template-functions.php:335
Stack trace:
#0 /home/webapps/oeglobal/wp-content/plugins/wp-discourse/lib/discourse-comment-formatter.php(136):
WPDiscourse\DiscourseCommentFormatter\DiscourseCommentFormatter->fix_avatars_in_quotes()
#1 /home/webapps/oeglobal/wp-content/plugins/wp-discourse/lib/discourse-comment.php(312):
WPDiscourse\DiscourseCommentFormatter\DiscourseCommentFormatter->format()
#2 /home/webapps/oeglobal/wp-content/plugins/wp-discourse/blocks/comments/comments.php(34):
WPDiscourse\DiscourseComment\DiscourseComment->comments_template()
#3 /home/webapps/oeglobal/wp-includes/class-wp-block.php(586):
render_block_wpdc_comments()
#4 /home/webapps/oeglobal/wp-includes/blocks.php(2359): WP_Block->render()
#5 /home/webapps/oeglobal/wp-includes/blocks.php(2431): render_block()
#6 /home/webapps/oeglobal/wp-includes/class-wp-hook.php(324): do_blocks()
#7 /home/webapps/oeglobal/wp-includes/plugin.php(205): WP_Hook->apply_filters()
#8 /home/webapps/oeglobal/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php(1967):
apply_filters()
#9 /home/webapps/oeglobal/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php(661):
WP_REST_Posts_Controller->prepare_item_for_response()
#10 /home/webapps/oeglobal/wp-includes/rest-api/class-wp-rest-server.php(1292):
WP_REST_Posts_Controller->get_item()
#11 /home/webapps/oeglobal/wp-includes/rest-api/class-wp-rest-server.php(1125):
WP_REST_Server->respond_to_request()
#12 /home/webapps/oeglobal/wp-includes/rest-api.php(586):
WP_REST_Server->dispatch()
#13 /home/webapps/oeglobal/wp-includes/rest-api.php(2973): rest_do_request()
#14 [internal function]: rest_preload_api_request()
#15 /home/webapps/oeglobal/wp-includes/block-editor.php(754): array_reduce()
#16 /home/webapps/oeglobal/wp-admin/edit-form-blocks.php(114):
block_editor_rest_api_preload()
#17 /home/webapps/oeglobal/wp-admin/post.php(187): require('...')
#18 {main}
thrown
```
---
### Author:  [@angus](https://meta.discourse.org/u/angus)
#### Post date: [October 20, 2025, 9:43am UTC](https://meta.discourse.org/t/critical-error-call-to-undefined-function-mb-convert-encoding/386125/2 "2025-10-20T09:43:50Z")
Hey Alan, you need php’s [mbstring](https://www.php.net/manual/en/book.mbstring.php) installed and enabled to run [WP Discourse](https://github.com/discourse/wp-discourse). Please ask your Wordpress site admin to install and / or enable it.
---
### Author:  [@system](https://meta.discourse.org/u/system)
#### Post date: [November 19, 2025, 9:44am UTC](https://meta.discourse.org/t/critical-error-call-to-undefined-function-mb-convert-encoding/386125/3 "2025-11-19T09:44:10Z")
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