The main goal of refactoring is clean code, better code, or whatever you might call it. But what actually constitutes good code? Good code is smelled and tasted. If you've written a lot of code, you understand what I mean; you can easily identify whether code is good or bad with experience. But what if you are new to coding but still want to do things right? We can summarize the aspects of good code with these three guidelines: Readable, Extensible and Efficient

He goes on to explain each of these three guidelines with descriptions of what they are and what they mean to you as a developer. In the next part of the series, he'll take these three ideas and apply them to code, showing some of the most common points where they can be applied to clean things up.

Our framework is still missing a major characteristic of any good framework: extensibility. Being extensible means that the developer should be able to easily hook into the framework life cycle to modify the way the request is handled.

He chooses the Observer design pattern as a basis for his example, allowing any kind of behavior/actions to be added to the framework's execution. He includes the Symfony2 dispatcher to make this work and includes the code for a "handle" method to fire off events. It executes a "ResponseEvent" every time the framework is executed. An "addListener" method provides the hook to apply a callback to an event - in his case an anonymous function (or closure).

As you may know, PHPExcel is built using an extensible model, supporting different input and output formats. The PHPExcel core class library features a spreadsheet engine, which is supported by IReader and IWriter instances used for reading and writing a spreadsheet to/from a file. Currently, PHPExcel supports writers for Excel2007, Excel5 (Excel 97+), CSV, HTML and PDF. Wouldnt it be nice if we could use PHPExcel to store a spreadsheet on Google Documents? Let's combine some technologies.

The two technologies in question are a standard install of the PHPExcel library and the Zend Framework (with its Zend_Gdata component). Using the component, a save() method is created and hooked into the IWriter interface of PHPExcel. When this save method is called, the Zend_Gdata component connects to the Documents service and uploads the resulting information for the account you supply.

Welcome to the final part of the series "Building an extensible website engine with PHP 5." In two tutorials, this series teaches you how to build a versatile website system which allows you to generate dynamic web documents by using a few simple PHP classes.

They demonstrate how to pull the contents of the page from the database to flesh out the content, push that data out into the page template itself, and, as a final step - they take a look at the entire system in action.

Over the course of this two-part series, I'll walk you through the development of a highly extensible and "pluggable" website engine with PHP 5, which will allow you generate web pages on the fly based on a predefined (but simple) database structure.

They start things off by setting up the core of the system - the layout and structure of how the pages will flow. To help make this an easy task, they also create the simple template with links down the side to the different "pages". Finally, they finish off this part of the series with the database structure and push some of the sample content in to give you an idea of how it's all formatted.

The tutorial walks you through the simple process, looking back at the simple version they made before, looking forward at expaning it to handle multiple client requests, and creating a "socket server" class to automatically handle the creation of the socket.

You'll need a bit of experience with templating your site before you get started, as they begin with a basic structure of the template processor before anything. They demonstrate the code to create the "TemplateProcessor" class and defining the "processTemplate" method inside it. By the end of this first part in the series, they've created a very simple templating class that could be used as is for base-level projects. Stay tuned for more, though, if you're hungry for more features.