The function mb_strlen() is not enabled by default in PHP (although many hostings and server packages have it enabled). Please read the manual for installation details:
http://www.php.net/manual/en/mbstring.installation.php
[quote:1xfsj0z6]Installation
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.
The following configure options are related to the mbstring module.[/quote:1xfsj0z6]
