What happens here is the natural lifecycle of programming languages. The languages are innovative and disruptive at the beginning, than they become mainstream and than they slowly fade out while new and better suited alternatives arise.
Java kind of disrupted C/C++, PHP with Apache &co. ate a big portion of Java's market. But I personally think tha PHP is also over it's peak and the new languages like Ruby with Rails, or the functional programming wave, are coming fast.
So, I see C/C++ and Java being on their 'legacy' or 'phase out' portion of their lifecycle when no more extraordinary new features are added but the old ones are very stable and widely used.
PHP may be only a little after it's peak. It is still fast evolving, but the downward trend can already be observed.