PHP is perfectly suited for small web development tasks, like to add some dynamic content to static pages without much overhead or setup.
The language is easy to learn and to handle, and can also be used to create command line scripts. (Instead of the more complicated Perl for example.)
However, PHP's history, evolving from a macro processor is still visible. While it supports OOP, the core of the language is not object oriented at all. And sadly, the developers let the major release PHP 5 pass without cleaning up the accumulated differently named functions with randomly ordered arguments.
We upgraded our website last year, and in doing so, moved to a combination of PHP and MySQL to power the site. We've found PHP to be an easy-to-grasp language.
PHP was my introduction to programming and I feel it is a good language for first-timers to learn. It needs understanding of HTML, which is an excellent starting point for any new programmer.
I agree with Rasmus's view that PHP is essentially a templating language as at it's most basic it generates HTML output. Unfortunately it's grown up as a spiderweb of libraries which has earned it a lot of criticism but these libraries are of good quality.
While it's loose typing and lack of order of it's functions may put off people used to .NET it's worth sticking with if you have time enough to learn your way around it.
Quite simply if PHP didn't exist I wouldn't have a job or maybe never have gotten into programming. Its a very easy language to use but difficult to master.
The PHP always getting better. It is very simple and have some interesting features. No doubt, PHP is the best solution for the Web development. It was created by Web for the Web. And it is evolving as fast as Web.