PHP can be put to many uses other than just generating reams of HTML. As a scripting engine to be called from the command line PHP is particularly popular, and this is likely to continue to grow.
You can create cross-platform graphical user interfaces using PHP, and even design them using a GUI tool in the form of Glade.
PHP is not all about work, work, work - you can make great games with PHP using only minimal effort.
If you really want to push your PHP learning curve, try writing your own language compiler. Yes, it is certainly hard work, but once you get the theory out of the way there is a lot you can do to exploit the power of PHP in your own new way.
We have covered only four alternative uses for PHP here - there are lots of others, so use your imagination!