Developers like it simple. PHP rose to it’s popularity because it was so straightforward and downright rewarding to start hacking away to get results.
Since those days PHP has grown up to be a mature and stable platform requiring quite a bit of knowledge to get into. It’s no longer the quick and dirty solution in the minds of developers, but rather the boring tool they used five years ago.
It seems like insanity; just as PHP is getting suitable for larger teams to work on big products it’s being killed off by WordPress? Now if only that was the case. Java continues to be around and popular because it has structure and is a astable platform.