I was in the process of adding a creation date to a set of 19 images I had just uploaded, and upon trying to save the changes, the page reloads and displays this message: `Fatal error: Uncaught Error: Call to undefined function mb_substr() in /path/topiwigo/admin/intro.php:397 Stack trace: #0 /path/to/piwigo/admin.php(346): include() #1 {main} thrown in /path/to/piwigo/admin/intro.php on line 397`.

The gallery site loads just fine, it's only trying to access the administration page where this error is displayed. This is all with php8.2.

EDIT: It looks like only the Dashboard page of the admin tools is inaccessible. Navigating directly with something like `admin.php?page=tags` works correctly.
Fatal error accessing administation page (14.0.0RC1)
This is a GitHub Issue
repo:Piwigo
owner:Piwigo
Title : Fatal error accessing administation page (14.0.0RC1)
Issue date:

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I was in the process of adding a creation date to a set of 19 images I had just uploaded, and upon trying to save the changes, the page reloads and displays this message: `Fatal error: Uncaught Error: Call to undefined function mb_substr() in /path/topiwigo/admin/intro.php:397 Stack trace: #0 /path/to/piwigo/admin.php(346): include() #1 {main} thrown in /path/to/piwigo/admin/intro.php on line 397`.

The gallery site loads just fine, it's only trying to access the administration page where this error is displayed. This is all with php8.2.

EDIT: It looks like only the Dashboard page of the admin tools is inaccessible. Navigating directly with something like `admin.php?page=tags` works correctly.
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