Use mb_strlen( $string, '8bit' ) instead of strlen( $string ) for cases of mbstring overloading functions. http://php.net/manual/en/mbstring.overload.php

git-svn-id: https://plugins.svn.wordpress.org/contact-form-7/trunk@1055253 b8457f37-d9ea-0310-8a92-e5e31aec5664