Nitro is a really easy to use, very customizable, and extensible ORM for CodeIgniter. It's pure PHP, which means you won't have to install any commandline tools to run it, just one mapping file (or as many as you like), which is as simple as defining a PHP array, and let Nitro create the classes and manage the relations.
PhpPeanuts is a framework for developing database-backed applications in PHP. Rather than building an application from the bottom up, you initially only build domain model classes in which you specify properties, relationships, and database table names in metadata. The framework dynamically scaffolds getters and setters, persistency, navigation over relations, and input and delete validation. The abstract user interface instantly offers a rich set of pages for searching, browsing, drilling down, editing and reporting over your domain model. From there on you extend and refine both the domain model and the user interface to make it what you want by defining specialization classes and overriding inherited methods.
pdoMap is a robust PHP ORM with many OOP features. The mapping structure, requests, and transactions are defined in XML files. The core directly generates PHP classes for high performance. It is very easy to use and configure. It features fully optimized code, caching data, a full lazy loading system, and an open system for extending all functionality.
DooPHP is a very fast PHP framework. It enables developers at all levels to rapidly develop robust Web 2.0 applications. It is quite feature rich. DooPHP supports some common stuff found in a Web framework, such as an MVC-base structure, RESTful APIS, a REST client, URI routing, database ORM tools, a model generator, HTTP Digest Authentication, a flexbible compiling template engine, logging and profiling tools, and more.