My last position involved the use of PHP 4 in a variety of different internet applications.

The first time I used PHP, I was required to convert a Perl site to PHP in ten days.  The conversion was easily done and effective.  PHP is one of those language that is easy to learnbut because it is easy to learn and implement it is possible to write convoluted code that can create security issues and performance issues for your web server, if you do not take the time to learn and understand all the nuances of the code.

Object oriented frameworks for PHP include:

POOF - PHP Object Oriented Framework

MVC Frameworks