The PHP Content Repository is an adaption of the Java Content Repository (JCR) standard, an open API specification defined in JSR-283.
The API defines how to handle hierarchical semi-structured data in a consistent way.
The typical use case is content management systems. PHPCR combines the best out of document-oriented databases (weak structured data) and of XML databases (hierarchical trees). On top of that, it adds useful features like searching, versioning, access control and locking on top of it.
PHPCR is targeted at semi structured content. For strictly structured content and when using aggregation queries, we recommend using relational databases.
For example: A web shop where products are stored in PHPCR, orders are stored in a relational database.
PHPCR defines the interfaces for content repositories. There are several implementations available that you can use: