Fatal error: Call to undefined function mb_strstr()

[TurboPT]

What system do you have?

For Fedora/Redhat, you might be able to install the lib in this manner:

yum install php-mbstring

...then restart the webserver after intallation is complete.

Of course, you will need to find the install command appropriate for your specific environment, if you do not have Fedora/Redhat.

The yum package manager is available on other linux environments too, try simply typing yum at the prompt to know if it exists, but you might have to first be sudo or root to run this command.