As a developer, you already know that many times, one programming language, platform, or technology just isn't enough to do the job right. Recently, there's been a lot of buzz and information about using PHP on the server side with Adobe Flex or AIR applications as the front end. You can use this technique to gain a lot of power and flexibility, and that's one of the topics I discuss in depth in this article. Sometimes, however, one interface isn't enough.

In my scenario, this is precisely the case. The scenario calls for a lightweight, cross-platform desktop application that does its job and stays out of the users' way. It also needs a powerful management interface that can be accessed from anywhere. To address both needs, you first create a desktop application for AIR that leverages PHP back-end services for persistent storage and extra horsepower. Then, you create a simple and quick PHP/Hypertext Markup Language (HTML) browser-based interface for management and output applications.

The time-tracking and billing system you create in this article is called Clocked! It is specifically designed for freelancers, contractors, and others who work on computers and need to track their time. To best address the needs of these users, Clocked! has the following requirements:

• Runs on Mac, Windows, and Linux. Because your users are running all of these platforms in more distributed proportions than regular computer users, you need to support all three.
• Easily track time in different increments. This feature is key; your users need a simple, intuitive, unobtrusive way to track their time that requires as little effort as possible. This whole project is predicated on the belief that their time is valuable, and you don't want to waste it.
• Store the information in a central location. Many of your users work in teams or as subcontractors, so information about their hours accrued needs to be accessible from anywhere.
• Organizes information in a natural way. Your users work on projects for clients and invoice those clients based on hours attributed to each project. The Clocked! application needs to organize all these entities (clients, projects, invoices, and time slips) in a logical way.

The best way to accomplish all these goals at the same time is to divide the feature set into two applications. The Clocked! application consists of a desktop application for time tracking and a web-based, PHP-driven interface for management.

Here's how this two-part approach meets your needs. You take care of the first two requirements at the same time. Because Clocked! runs on AIR, users on Windows, Mac, and Linux can use it. AIR applications also run on the desktop, so users can launch and run the program without opening a separate browser window or tab. Finally, AIR applications run in an Adobe Flash Player-based environment, so you can give your users a sleek, unobtrusive interface with ease.

Because the management side of Clocked! is a web application, managers and users will be able to access Clocked! data from any web browser. Using PHP allows you not only to create a fast, lean application quickly, but you also gain the ability to communicate with the AIR-based client efficiently. The Zend_Amf extension of the Zend Framework allows native Action Message Format (AMF) communication between AIR applications and PHP services, which means that server calls will be as fast as possible, and you'll be able to leverage the full power of PHP when dealing with data from the desktop clients.

Finally, you have to plan carefully to make sure the data structures in Clocked! make sense. You do that by clearly defining all of your objects-clients, projects, invoices, and time slips-and organizing them both in the code and in the MySQL database you'll be using for persistent storage.