Well if you looked at my se3.org site you may have read that I've been developing web applications for about 5 years now. In that time I've written a little bit of everything, PHP,ASP, ColdFusion and even some Perl. For many years there has always been a demand for ASP or ASP.NET applications. In the last few years I have more demands for Applications that are more Paltform-Independent. Many Clients are finding it more cost effective to change their servers to Linux or Unix. Because of this they are finding their old ASP applications aren't very friendly to Linux and Unix.
PHP seems to be the language in demand these days. Unlike many language PHP is easy to install and configure. PHP is avaliable for many flavors of Linux and Unix, and for you Microsoft nuts, even Windows. PHP works well with many Databases, most notably MySql, a robust opensource database. PHP also works with popluar Server software such as Apache and IIS.