This git repository helps you get up and running quickly w/ a PHP sample application that uses MongoDB on OpenShift

Create an account at http://openshift.redhat.com/

Create a php-5.3 application

rhc app create -a phpmongotweet -t php-5.3

Add MongoDB support to your application

rhc app cartridge add -a phpmongotweet -c mongodb-2.0

Add this upstream phpmongotweet repo

cd phpmongotweet
git remote add upstream -m master git://github.com/openshift/phpmongotweet-example.git
git pull -s recursive -X theirs upstream master

Then push the repo upstream

git push

That's it, you can now checkout your application at: http://phpmongotweet-$yourlogin.rhcloud.com