mbstring_check_encoding() in cache database backend doesn't actually work

Created on 30 August 2015, almost 10 years ago

Updated 10 August 2025, 13 days ago

Problem/Motivation

When installing Drupal 8 on a system that does not have mbstring support, a fatal error is thrown after the database has been created, as the cache module uses mb_check_encoding in the normalizeCid function, without checking for existence of that function.

Fatal error: Call to undefined function Drupal\Core\Cache\mb_check_encoding() in core/lib/Drupal/Core/Cache/DatabaseBackend.php on line 410

As mbstring is not a requirement (the installer system check gives a warning if mbstring is not present, not an error), the module should either check to see if it's present, or not use it at all.

Steps to reproduce:

make sure mbstring is disabled
follow install.php
after entering the database details, the error is thrown

Proposed resolution

Add a method in DatabaseBackend to check for the existence of mbstring, and use a regular expression match to determine if the CID is ASCII instead. This allows for the non-mbstring functionality to be tested on testing infrastructure with mbstring installed. The DatabaseBackend unit tests should be expanded to cover this case.

Remaining tasks

Write patch with tests in DatabaseBackendUnitTest
Review patch
(done)

User interface changes

None

API changes

An internal method is added to the cache DatabaseBackend.

Data model changes

None.

Beta phase evaluation

🐛 Bug report

Status

Needs work

Version

11.0 🔥

Component

cache system

Created by

TomCan

Live updates comments and jobs are added and updated live.

cache

database cache

mbstring

Bug Smash Initiative

Incomplete comments

Comments & Activities

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Comment 13 days ago →

sboden

I just upgraded from Drupal 10 to Drupal 11.2.3, and I still get the error:

Deprecated function: mb_check_encoding(): Calling mb_check_encoding() without argument is deprecated in Drupal\Core\Cache\DatabaseBackend->normalizeCid() (line 501 of core/lib/Drupal/Core/Cache/DatabaseBackend.php).
Drupal\Core\Cache\DatabaseBackend->normalizeCid() (Line: 120)
Drupal\Core\Cache\DatabaseBackend->getMultiple() (Line: 110)
Drupal\Core\Cache\DatabaseBackend->get() (Line: 326)
Drupal\Core\Cache\CacheCollector->lazyLoadCache() (Line: 144)
Drupal\Core\Cache\CacheCollector->get() (Line: 112)

Comment 13 days ago →
sboden
The patch for Drupal 11.2.3, possible Drupal 11.x
Comment 13 days ago →
🇬🇧United Kingdom catch
mb_check_encoding() shouldn't be called without arguments - that suggests NULL is being passed as a cache ID?

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