On NetTuts.com there's a new article posted that introduces you to the concept of a persistence layer in a PHP application:

One of the most confusing design pattern is persistence. The need for an application to persist its internal state and data is so tremendous that there are likely tens - if not hundreds - of different technologies to address this single problem. Unfortunately, no technology is a magic bullet. [...] In this tutorial, I will teach you some best practices to help you determine which approach to take, when working on future applications. I will briefly discuss some high level design concerns and principles, followed by a more detailed view on the Active Record design pattern, combined with a few words about the Table Data Gateway design pattern.

Included in the post is a high-level application design with the business logic is at the core and the persistence technology/layer exists outside of it. They show how to create a simple, working solution for a persistence layer to handle a blog post and its contents. It talks about characterization tests, the table gateway design pattern and the possible move to the active record pattern.

On the Zend Developer Zone there's a new post sharing the latest episode of their ZendCon 2010 sessions series - a talk from Stefan Priebsch about object persistence in PHP.

The object-relational impedance mismatch makes persisting PHP objects in a relational database a daunting task. How about these new schemaless NoSQL databases? We will have a look at the problems involved with persisting PHP objects, and introduce design patterns that help solving these problems. Putting the patterns to good use, we will build a working PHP object persistence solution for MongoDB.

You can download the episode as an mp3 and follow along with the slides for a more complete picture.

On the Zend Developer Zone today, there's a new post about a new project that's been launched - an object persistence layer for PHP, Junction.

The goal is to automate basic query construction, decouple the application from the database, and allow for faster development. With Junction you write a simple data object (the only requirement is that it have getters and setters) and a mapping file, following that you can start interacting with the database.

The project is completely open source (under the MIT license) and is operating under the "release early, release often" mentality. You can grab this most recent download directly from their site.

In his latest entry, Alexander Netkachev explains how to install the Propel object persistence layer and it's needed packages into your PHP application.

Object persistence layer provides the developers with the API that allows them to operate with data of the application in object-oriented manner. The developers can use known OOP methods for searching for and restoring the objects from the database. Something like this you can find on the main page of the Propel project and in the Wikipedia article about ORM technology.

These enthusiastic words roused my interest in the technology and I promised myself I would spend some time on testing a software for generating object persistence classes. And I ready to try the Propel library, because it is used by the Symphony framework, which I plan to test in a couple of weeks.

He starts with a little background information about why he's chosen to go with Propel and the process he followed to get things up and running smoothly. He links to the software you'll need (Propel, Creole, and Phing) and gives the install structure and environment variables you'll need to set. Finally, he gives an example .bat file to help perform the install automatically, reducing the problems that could happen when done manually.

Harry Fuecks mentions an interesting project today on the SitePoint Blog - CouchDb - a stand-alone document store, accessible via XML REST.

Firing up the CouchDb server on Windows is a breeze-follow the README. PHP-wise, you need the new http extension which is most easily done on Win32 by grabbing the most recent PHP 5 release (5.1.6) and the corresponding collection of PECL modules.

The interface between CouchDb and PHP is REST - XML + HTTP - you can also point your browser directly at the CouchDb server (default - localhost:8080) and get around with a little help from the CouchDb wiki.

So, if it's Just Another Database, why should we pay attention? Harry notes (with a code example) that it's more about how it stores the information and not just that it does. His example takes in a POST request from a form and pushes it (raw data) into the CouchDb functions. He also gives an example of where this would be handy - in a wiki (like Dokuwiki) where the files are currently stored on the filesystem instead of in a database.