1.2 Required skills

PHP OOP

First you need a some programming skills :). We recommend the courses from teamtreehouse.com:
https://teamtreehouse.com/tracks/php-development

They are not free, but they have a 14-day trial.

Symfony basics

You need to learn Symfony first. You can find a good tutorial at:
http://www.intelligentbee.com/blog/tag/symfony2-jobeet/

After that it is also recommended to read the Symfony Cookbook:
http://symfony.com/doc/current/cookbook/index.html

MongoDB ODM

As Integrated uses MongoDB heavily we recommend to have some knowledge about it. 

We recommend the Doctrine MongoDB ODM documentation:
http://doctrine-mongodb-odm.readthedocs.org/en/latest/

Working with Composer

Integrated uses Composer for package management. You need to know some composer basics. We recommend this courses from teamtreehouse.com:
http://teamtreehouse.com/library/php-standards-and-best-practices

They are not free, but they have a 14-day trial.