Nodes and Relationships

Working with Nodes

Nodes are the first of the two major entity types in a graph database. A node is a collection of zero or more key-value pairs. Neo4jPHP makes it very easy to create and work with nodes.

Create a Node

The following code snippet creates some nodes, sets some properties on each, and saves the nodes to the server. The $client variable was created according to Introduction - Creating a Connection to Neo4j.

$arthur = new Everyman\Neo4j\Node($client);
$arthur->setProperty('name', 'Arthur Dent')
    ->setProperty('mood', 'nervous')
    ->setProperty('home', 'small cottage')
    ->save();

$ford = new Everyman\Neo4j\Node($client);
$ford->setProperty('name', 'Ford Prefect')
    ->setProperty('occupation', 'travel writer')
    ->save();

$arthurId = $arthur->getId();

Each Node::setProperty() call returns the Node object, allowing the calls to be chained together fluently.

Node::save() will return true if the Node was saved successfully to the server, or false otherwise. If the save was unsuccessful, Client::getLastError() will return a diagnostic error code to aid debugging.

Retrieving a Node by ID and Updating

Now that the node has been created, the node's id can be used to retrieve the node from the server later. The following code retrieves the node and prints its properties:

$character = new Everyman\Neo4j\Node($client);
$character->setId($arthurId)
    ->load();

foreach ($character->getProperties() as $key => $value) {
    echo "$key: $value\n";
}
// prints:
//   name: Arthur Dent
//   mood: nervous
//   home: small cottage

$character->removeProperty('mood')
    ->setProperty('home', 'demolished')
    ->save();

foreach ($character->getProperties() as $key => $value) {
    echo "$key: $value\n";
}
// prints:
//   name: Arthur Dent
//   home: demolished

The call to Node::load() will return true or false depending on if the node was loaded successfully or not.

Node::getProperties() returns an array of all properties on a node, keyed by the property name. Individual properties can be retrieved with Node::getProperty and removed completely with Node::removeProperty(). Any changes to the node will not be persisted to the server until Node::save() is called again.

Delete a Node

A node can be deleted as long as its ID has been set.

$earth = new Everyman\Neo4j\Node($client);
$earth->setId(123)
    ->delete();

Node::delete() will return true if the Node was deleted successfully from the server, or false otherwise. Note that it is unnecessary to call Node::load() before deleting. Supplying a valid ID is good enough.