I've ran into an issue with my PHP mapper script where an PHP extension I needed was missing. These are the extensions available that mapreduce instances start with by default.
hadoop@ip:~$ php -m
In order to add specific PHP extensions that you need you have to create a bootstrap script that Amazon will run before your jobs.
As an example if you want to install PHP cURL extension crate a install-script.sh file and put code bellow in it.
sudo apt-get -y install php5-curl
This will install php extension and not ask any questions. Now all you need is to put this script in your S3 bucket and tell Amazon to run this as a bootstrap script. If you start your jobs via Amazon console you can do that on Bootstrap actions step or if you use Amazon Elastic MapReduce ruby client add
to your commands.