Server-side scripting and PHP

Server-side scripting is a web server technology that replaces the use of static, unchanging HTML pages with dynamically generated HTML pages. The pages are generated by scripts on the server (hence the name) when requested and passed back to the browser.

These dynamically generated pages have a number of significant benefits over static pages:

There are many different languages that can be used for server-side scripting, but since Joomla! uses PHP, so we will be focusing our studies there.

A dynamic, PHP powered, site's structure differs from a static web site in several key ways:

Joomla!, like most PHP sites, uses the file index.php as the primary gateway to a site. This file receives the requests from the browser and then calls the appropriate PHP functions needed to create a page that matches the request. However, please note that we will usually never change any of the code inside a Joomla! site's index.php file because all it does is call other files, many of these are template or extension files. It is the template and extension PHP files that we will usually be editing.

As mentioned above, most PHP generated sites, including Joomla! use a database to store their raw data. This makes it much easier, and faster, to retrieve data when it is requested by the user. It also allows powerful data operations and functions to be performed on the data if needed, such as aggregating it, sorting it, or making it easier to read.

The most common database for PHP sites, and the one used by Joomla! is MySQL. It is popular because not only is it open source and requires no cost to download and install, but it is also very reliable and powerful.

PHP code is designed to operate in two main methods. First, it can be run as complete PHP file. Usually these files are used for data processing, function declarations, or other unseen work.

The other method is to embed PHP into HTML code, usually to add loops, conditions, and load data into the otherwise static HTML, and usually these mixed HTML/PHP files are used as templates, or parts of templates, for displaying data on a site.

PHP can be easily recognized by the telltale <?php … ?> tags around sections of code. These tags are needed to complete PHP files and appear at the very start and end of the file. However, in a mixed HTML/PHP file, there are usually many, shorter code sections and tags.

The basic operation of a Joomla! site revolves around the index.php file, calling the PHP files for the extensions and template required by the client request, and then assembling the HTML code output by them into a page and then sending it to the client. Extension PHP files usually reside in a /components/com_componentname directory, /modules/mod_modulename, or /plugin/plugintype/plg_pluginname and templates in a /templates/templatename folder.