PHP Fatal error: Call to undefined function mb_detect_encoding()

How to fix this error

PHP Fatal error:  Call to undefined function mb_detect_encoding()

when trying to use the mb_detect_encoding PHP function

This means that the php-mbstring extention needs to be installed

To install this on a Centos server run the following command from the command line

yum install php-mbstring

and then restart the Apache web server by using this command as root

service httpd restart