It may seem strange to some readers that we are introducing a revised version of the Learn Joomla! Book for Joomla! 1.5 nearly six months after the release of Joomla 1.6. However, there are a number of good reasons why many website developers are staying with Joomla!1.5 even for new websites at present.

These come down to four main factors:

1. Extension support. While there are now 1,825 extensions compatible with version 1.6 according to the Joomla official extensions directory, this is much less than the total 7,688 extensions currently listed, which are generally all compatible with Joomla! 1.5. There are a number of significant extensions which have not yet been released for version 1.6, including Virtuemart, the most popular shopping cart solution for Joomla! and K2 the blogging environment. If you need an extension which doesn't work with Joomla! 1.6 yet then you need to stick with Joomla! 1.5 for now

2. Joomla! has moved to a time based release approach for new editions of Joomla. Joomla 1.6 has a significant number of changes 'under the bonnet', and the idea is to move away from big new version releases every three years to a new version release every six months. This is a new concept in Joomla! development, and to be frank the jury is out on whether it will work out and whether it will become the established way things are done. As mentioned above a number of larger extension developers are hanging back to see what happens in July 2011 with the new release. This is also an issue for anyone thinking of building a new website with Joomla 1.6.

3. Whenever a new version of software comes out, it takes a while before the bugs and security holes are discovered, resulting in a number of version upgrades being released quickly. Experienced developers often hang back from a few months until most of the problems and bugs have been identified by the early adopters and fixed, thus avoiding quite a lot of wasted time.

4. There is no simple upgrade process to move from version 1.5 to version 1.6, because of the major underlying changes to the software architecture, it requires a 'migration' i.e. significant manual work from the developer.

So hopefully, I have explained why Joomla 1.5 is still important. Finally it is important to note that Joomla have indicateded that security releases for Joomla 1.5 will be continued until at least April 2012 at the earliest.

So what's changed in the Joomla 1.5 world, which requires a new revised edition of Learn Joomla 1.5? Essentially it is the third party extensions. Joomla itself is largely unchanged, apart from being a later version number (1.5.23 at time of writing), for reasons of security hole fixes and bug fixes.

When the second edition was written Joomla 1.5 was still pretty new and many of the extensions newly ported across. Kunena has now taken over as the integrated Forum solution of choice from Fireboard, essentially it is a forked and heavily developed version of Fireboard. DocMan is now a commercial extension and we have replaced it with JoomDoc, a forked version of the extension, but virtually identical, because we only recommend 'free/non-commercial extensions' in this book. Many of the other extensions originally recommended in Chapter 8 of the second edition of Learn Joomla! have not been developed further and new ones have taken over as the popular solution, e.g. we have replaced Smart SEF by Artio SEF, and yvComment by jComments. Acajoom News is now jNews and so on. We have also added a new section explaining how to do Backups and restore sites to new locations, using Akeeba Backup, an extension which is now very popular, and we have also recommended a couple of other very good extensions we have worked with: Fabrik, a form builder and EventList an events listing extension.

Joomla continues to be a very popular Open Source content management system, very largely because of the huge and vibrant ecosystem of third party developers which has developed around the core software. As long as this community continues to thrive and grow, Joomla will maintain it's position as one of the most important content management systems for mainstream website development.

Hope you enjoy the book and find it useful!