As you may noticed I use WordPress for my blog. This is an unbelievable great piece of software. It has uncountable possibilities for enhancements and as soon as you begin to explore these, you start adding some of them to your own blog. One of the plugins I added was WPtouch. This plugin wraps your blog into a theme for mobile devices if they are detected. This works for the iPhone, the Android platform or even Palms webOS. The theme is styled in a way it makes the content more readable on such (screen) limited devices and moves the menus to some extra place.

Why writing a plugin if there are so many

On our web server we are using Power PHLogger for a simple user statistic tracking. Unfortunately this software isn’t maintained anymore, but it does it job very well. To use it you have to embed some JavaScript code and a blind image to every website you want to track. My first try was to add this code to the theme I use. This worked ok, but I soon realized that this has to be done on every update of the theme. Additionally this doesn’t work with plugins like WPtouch, as there the whole theme is replaced. I searched for a plugin which takes this job, but I didn’t find one. So what, I’m a programmer, time for writing it myself.

Creating the necessary bits of code

Plugins in WordPress are located at the wp-content/plugins directory below the WordPress installation path. You have to choose a name, I used phlogger, and create a directory with that name. The plugin itself is written in PHP and named like the directory with the php extension. As the title says, it’s a simple plugin with one public method only, as shown in the following code.

<?php
/*
Plugin Name: phlogger
Plugin URI:
Description: Adds the power phlogger code to the footer.
Version: 0.1
Author: Christian Pötzsch
Author URI: http://www.64k-tec.de
*/

add_filter('wp_footer', 'phlogger_footer');

function phlogger_footer()
{
 $l = '<script type="text/'."n".'mce:1'."n";

 echo $l;
}
?>

The method just outputs the code for the phlogger tracking. WordPress executes this method because of the add_filter call. wp_footer is the filter keyword for content which should be added to the footer of a webpage, just before the </body> tag. The comment on the top of the file isn’t only there for cosmetic reasons. It’s parsed by WordPress and shown in the Plugin admin page of your blog settings. So it have to be there.

Of course I could have been adding methods for setting the phlogger link or the user name, but for my case this wasn’t necessary. For more information on writing WordPress plugins have a look at the good documentation.

Conclusion

Starting to write WordPress plugins is easy. It makes even sense for so simple tasks like this, because it offers the possibility to inject code (and functionality) without changing WordPress or the theme itself.