This is Part 2 of a series on setting up a development environment for building projects using the graph database Neo4j and PHP. In Part 1 of this series, we set up unit test and development databases. In this part, we'll build a skeleton project that includes unit tests, and a minimalistic user interface.

The post includes the code to create the testing harness, a bootstrap file and a basic test to handle the checks on deletion of an "Actor". The rest of the post shows how to use the connection to find an Actor based on input from the user via a form.

The thing that makes graphing databases useful is the ability to find relationship paths from one node to another. There are many algorithms for finding paths efficiently, depending on the use case.

He includes some code showing the REST request (made via this client) to fetch these street-based relationships. He then creates a little sample script that provides driving directions from one intersection to another with a "findPathsTo" call. He modifies it a bit later on to use the Dijkstra algorithm.

Lately, I've been playing around with the graph database Neo4j and its application to certain classes of problems. Graph databases are meant to solve problems in domains where data relationships can be multiple levels deep. [...] As you continue to add degrees, the query becomes increasingly unwieldy, harder to maintain, and less performant.

Graph databases, like Neo4j, handle these sorts of needs perfectly. There wasn't an official PHP interface for it, so he decided to create his own that worked with the REST interface the database provides. He includes a few code snippets showing how to connect and make a few requests - setting properties on objects, relating objects to one another and making queries that follow the paths from user to user and return them as a simple array.