Hi.
I would like to why sitepoints always publish books regarding PHP. Why this focus on PHP? Even in the forum the first programmign language in the category is PHP. Anyone knows? 
I think this page gives a good impression why: Program Your Site - SitePoint Forums.
The PHP forum has the most threads and posts.
I also think it has to do with the cheap availability of PHP hosting and the ease with which people can start working with PHP.
23 books, 1 is about PHP, 1 about Wordpress.
29 ebooks, 2 are about PHP, 1 about Wordpress.
Why do you think they’re always publishing books about PHP?
I mean regarding server side languages, do they publish something about Ruby? about Python? about C#?
Simply Rails 2 - SitePoint Books
The ASP.NET 2.0 Anthology: 101 Essential Tips, Tricks & Hacks - SitePoint Books
Build Your Own ASP.NET 3.5 Web Site Using C# & VB, 3rd Edition - SitePoint Books
Didn’t find anything about Python and C#.
You didn’t? Look at the last two books you linked to 
oops… 