I also notice that doing a search on amazon.com gives me the following 
counts on books devoted to the frameworks you found.  I did an advanced 
search for "php" as a keyword and the framework name in the title.  Zend 
results for other Zend products (PHP cert training and Zend Studio) were 
filtered out.

CodeIgniter 3 (1 of those a brief on a special subject)
Symfony 1
CakePHP 2 (removing one in German)
Zend Framework 3 (1 of those available for pre-order)

There is another alternative for PHP developers interested in using an 
MVC framework.  If I were in that position, I'd check out "Rails for PHP 
Developers" in the Pragmatic Programmers series.

Chris

Cloutman, David wrote:
> This morning I was curious to see how the battle for domination between
> PHP frameworks was shaping up, and which one was most economically
> sensible for a developer with limited time to learn. I thought I'd share
> my results with the list, as this may be of interest to some of you.
>
> To gauge the demand for knowledge of particular frameworks, I did an
> informal survey of job descriptions on the SF Bay Area Craigslist's job
> posting. (I did not look act gigs--computers.) I entered the query "php
> framework" and got 38 results. Of these, I threw out results that were
> looking for someone to work primarily in another language (such as C#,
> Java, Python, etc.) or doing something not particularly PHP oriented,
> such as client-side development. I also threw out duplicates (there were
> several) and positions where the word framework was used to refer to
> something else, such as the LAMP technology stack, or an aspect of the
> application to be built. I eliminated 18 positions, leaving me with 20
> descriptions.
>
> For my purposes, I defined a framework as a piece of prebuilt software
> that facilitates the development of Web applications using the MVC
> design pattern. Smarty (a template engine), Doctrine (a standalone ORM
> utility), and Drupal were described as frameworks twice, once, and once,
> respectively. Utilities for other languages such as Spring, Hibernate,
> and Django also generated hits, but were not counted. If the job was
> clearly a PHP job and mentioned knowledge of a framework or MVC design
> patterns as desirable, I counted it as "Unnamed". If more than one
> framework was mentioned, I tallied each one named. In those cases, no
> job description surveyed named which framework the company used or
> favored.
>
> The results were pretty lopsided:
>
> Unnamed: 8
> Zend: 11
> CakePHP: 4
> Symfony: 4
> Code Igniter: 2
>
> Overwhelmingly, if only one framework was specifically named, it was
> Zend. 
>
> I also did a tally of JavaScript libraries named in qualifying
> positions. The results are:
>
> JQuery: 4
> Prototype / Scriptaculous: 3
> Yahoo! UI: 1
> ExtJS: 1
> Dojo: 1
>
> Given my small sample size, I don't think these results are quite as
> conclusive.
>
> - David
>
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