Elastica is a PHP client for the elasticsearch search engine/database. Elasticsearch is an Open Source (Apache 2), Distributed, RESTful, Search Engine built on top of Apache Lucene.
Elastica is open source, and you can download or clone the source code from ruflin/Elastica.
These instructions give you an overview of how to use Elastica. You can find the complete API here. It is build directly from source.
Credits
Credits go to all users that gave feedback and committed code.