PHP Fatal error: Uncaught Error: Call to undefined function mb_internal_encoding()
<p>I have this error message in my logs and I don't see how to solve it</p>

<p>PHP Fatal error:  Uncaught Error: Call to undefined function mb_internal_encoding()</p>

<p>Let me give you a bit of context:
I am running an nginx server with PHP7 FPM.
I did an apt-get update and apt-get upgrade and this function does not work anymore.</p>

<p>My phpinfo indicates mbstring is enabled</p>

<pre><code>mbstring
Multibyte Support   enabled
Multibyte string engine     libmbfl
HTTP input encoding translation     disabled
libmbfl version     1.3.2
oniguruma version   5.9.6 
</code></pre>

<p>php -m indicates mbstring and gd are installed and enabled</p>

<pre><code>toto@vps21:/var/www/html# php -m
[PHP Modules]
apc
apcu
bz2
calendar
Core
ctype
curl
date
dom
enchant
exif
fileinfo
filter
ftp
gd
geoip
gettext
gmp
hash
iconv
igbinary
imagick
imap
interbase
intl
json
ldap
libxml
mbstring
mcrypt
memcached
mongodb
msgpack
mysqli
mysqlnd
odbc
openssl
pcntl
pcre
PDO
pdo_dblib
PDO_Firebird
pdo_mysql
PDO_ODBC
pdo_pgsql
pdo_sqlite
pgsql
Phar
posix
pspell
readline
recode
redis
Reflection
session
shmop
SimpleXML
snmp
sockets
SPL
sqlite3
standard
sysvmsg
sysvsem
sysvshm
tidy
tokenizer
wddx
xdebug
xml
xmlreader
xmlrpc
xmlwriter
xsl
Zend OPcache
zlib

[Zend Modules]
Xdebug
Zend OPcache
</code></pre>

<p>and I run this version of php</p>

<pre><code>toto@vps21:/var/www/html# php -v
PHP 7.0.8-1~dotdeb+8.1 (cli) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2016 Zend Technologies
    with Zend OPcache v7.0.8-1~dotdeb+8.1, Copyright (c) 1999-2016, by Zend Technologies
    with Xdebug v2.4.0, Copyright (c) 2002-2016, by Derick Rethans
</code></pre>

<p>Do you have any idea to suggest because I don't understand where the error comes from...</p>

<p>Many thanks</p>