In his <a href="http://perens.sourcelabs.com/articles/2005/12/07/bruce-perens-forecasts-for-2006>latest post, some predicitons for 2006, Bruce Perens talks a little bit about the future of PHP and how things might take a turn for the worse.
PHP has become the BASIC of web application design, used primarily by designers without too much computer science background. The platform hasn't taken well to multiprocessing, and is doing poorly enough from a security standpoint that "PHP security" conferences have been hastily organized. PHP's woes aren't so much a problem with the PHP core as with existing libraries and applications on top of PHP and their lack of future-proofness. If PHP is to be faulted, it is because the platform designers never placed an emphasis on good software design by their users - for example, most PHP developers don't write using a model-view-controller paradigm.
While organizations invested in PHP will band-aid their existing code, new projects will move to other platforms, with designers more cognizant of both software engineering and application security.
Personally, I think that PHP, while not to the point he mentions here yet, is growing to that point rather quickly. More and more I see highly skilled PHP developers out there coming out with quality projects/products to help "the little guy" get up and running - *and* work within some standards...