In the context of Bitrix, the directive mbstring.func_overload is a setting often required by older versions of the Bitrix CMS (or self-hosted editions of Bitrix24). This setting ensures proper handling of multibyte strings, particularly for languages like Russian or other Cyrillic-based languages, which are common in Bitrix implementations.

How Bitrix Uses mbstring.func_overload

  1. Purpose:
    • Bitrix may rely on multibyte-safe string functions (e.g., mb_strlen() instead of strlen()).
    • The mbstring.func_overload directive ensures that PHP automatically substitutes standard functions (like strlen()) with multibyte-aware equivalents.
  2. Required Setting:
    • Some versions of Bitrix require mbstring.func_overload = 2 in php.ini for proper functioning.

Setting mbstring.func_overload for Bitrix

Enable in php.ini

1

Open your PHP configuration file

sudo nano /etc/php/{version}/apache2/php.ini # For Apache
sudo nano /etc/php/{version}/cli/php.ini # For CLI
2

Look for the mbstring.func_overload directive or add it if missing

mbstring.func_overload = 2
3

Restart your web server

sudo systemctl restart apache2 # For Apache
sudo systemctl restart php-fpm # For Nginx

Bitrix-Specific Notes:

  • Bitrix Admin Panel: You may see a warning in the admin panel if mbstring.func_overload is disabled or improperly set.
  • If Bitrix does not explicitly require mbstring.func_overload, you can safely omit it, especially if using PHP 7.2+ (since it is deprecated).

What to Do in PHP 7.2+ or 8.0 (When mbstring.func_overload Is Removed)

1

Upgrade Bitrix

  • Ensure you are using the latest version of Bitrix CMS or Bitrix24 that supports modern PHP versions.
  • Older Bitrix versions may still rely on this deprecated directive.
2

Manually Use mb_* Functions

  • Instead of relying on mbstring.func_overload, Bitrix developers should update their code to use mb_strlen(), mb_strpos(), and similar functions directly.
3

Disable the Directive

  • Remove the mbstring.func_overload directive from php.ini and test Bitrix for compatibility with PHP 7.2+.

Check mbstring.func_overload Compatibility with Bitrix

1

Run the Bitrix Environment Check Script

  • Bitrix provides a check script (bitrixsetup.php) to verify server compatibility.
  • Upload the script to your server and run it via a browser:
    • http://yourdomain.com/bitrixsetup.php
  • Look for any warnings about mbstring.func_overload.
2

Check PHP Logs

  • Look for errors in PHP logs related to mbstring.func_overload:
    • tail -f /var/log/php_errors.log

Troubleshooting

Issue Solution
Bitrix warns about mbstring.func_overload Enable it in php.ini or contact Bitrix support for an updated version.
PHP 7.2+ shows deprecation error Remove the directive and ensure Bitrix code uses mb_* functions explicitly.
Multibyte string issues (Cyrillic) Set mb_internal_encoding("UTF-8"); in your Bitrix configuration or in init.php.

Example PHP Configuration for Bitrix

Here is a recommended snippet of php.ini for Bitrix with mbstring.func_overload:

[mbstring]
mbstring.language = Neutral
mbstring.internal_encoding = UTF-8
mbstring.http_input = auto
mbstring.http_output = UTF-8
mbstring.encoding_translation = Off
mbstring.func_overload = 2