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php – Unable to call the built in mb_internal_encoding method?

Posted by: admin April 23, 2020 Leave a comment


I’m trying to install indefero on a CentOS 5.3 VMware ‘box’ and I ran into a problem.
Quite early in the installation I get an error that I’ve been able to narrow down to this:

[[email protected] /var/www/html]# cat x.php
[[email protected] /var/www/html]# php x.php
PHP Fatal error:  Call to undefined function mb_internal_encoding() in 
/var/www/html/x.php on line 2

I get the same error when calling this script via http through Apache.
Now according to the PHP manual the mb_internal_encoding function should be a builtin in PHP 5.

I have CentOS 5.3 i386 (Linux code 2.6.18-53.1.21.el5 #1 SMP Tue May 20 09:34:18 EDT 2008 i686 i686 i386 GNU/Linux) and I’ve installed PHP 5.2.9.

[[email protected] /var/www/html]# php -v
PHP 5.2.9 (cli) (built: Jul  8 2009 06:03:36)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies

I double checked: selinux has been disabled (for now).

How do i fix this?

How to&Answers:

mbstring is a “non-default” extension, that is not enabled by default ; see this page of the manual :


mbstring is a non-default extension.
This means it is not enabled by
default. You must explicitly enable
the module with the configure option.
See the Install section for details

So, you might have to enable that extension, modifying the php.ini file (and restarting Apache, so your modification is taken into account)

I don’t use CentOS, but you may have to install the extension first, using something like this (see this page, for instance, which seems to give a solution) :

yum install php-mbstring

(The package name might be a bit different ; so, use yum search to get it 🙂 )


For Debian/Ubuntu:

sudo apt-get install php7.0-mbstring


If someone is having trouble with installing php-mbstring package in ubuntu do following

sudo apt-get install libapache2-mod-php5


If you don’t know how to enable php_mbstring extension in windows, open your php.ini and remove the semicolon before the extension:

change this


to this


after modification, you need to reset your php server.


For OpenSUse (zypper package manager):

zypper install php5-mbstring


zyper install php7-mbstring

In the other hand, you can search them through YaST Software manager.

Note that, you must restart apache http server:

systemctl restart apache2.service