In the past few years ORMs have become increasingly popular; however I, personally, don’t like most of the ORM libraries.
ORMs are used to map data from the database to access it easily, and generally they do make it easier than regular SQL.
Nevertheless, these libraries are usually very heavy (Doctrine is almost 2MB!) and they enforce you to learn their complex usage (take a look at Doctrine’s documentation).
In contrast there is NotORM written by Jakub Vrána, which is a library for manipulating databases.
It is very easy to learn, you don’t have to create a class for every table in your database, and it handles table’s relationships sometimes faster than native PDO!
I won’t explain in this quick tip about NotORM, but you can read more about it in NotORM’s website.