Traditional relational databases like MySQL or Postgres are really good at providing many solutions to the problem of persisting state. But these types of database are really horrible at querying highly connected models in an efficient way.
Graph databases like Neo4j and OrientDB excel at highly connected data. In fact, graph technologies are the backbone of social networks like Facebook and Twitter. We discuss how to think about our data using the graph model and what tools we can use in our PHP projects to interface with them. We also discuss the considerations we'll need to make when deciding whether or not to use a graph database in our next project.