What is this?
This is sample application which is running on Heroku. Pure Heroku php doesn't support mbstring.
This sample is challenging to use mbstring as shared library.
What I did
heroku run bash allows to run command on heroku.
I did it steps bellow same as mongodb practice.
mkdir tmp cd tmp git clone https://github.com/php/php-src.git cd php-src git checkout php-5.3.10 cd ext/mbstring /app/php/bin/phpize ./configure --with-php-config=/app/php/bin/php-config make