Did you know you can use custom PHP extensions on Heroku? Neither did I, cos I can’t find it in the documentation. But you can:

https://gist.github.com/1288447

I came across this while searching for a way or workaround to use the MongoDB PECL extension on Heroku (don’t get me started on that…).

If you can’t be bothered checking the link, the summary is this:

1. Create a folder in your app called ‘ext’ or similar.
2. Copy your extension into this folder.
3. Create a php.ini file with the following contents:

   extension_dir = "/app/www/ext/"
   extension=mongo.so
   

4. Deploy