I know it's in vogue to hate on PHP,
I don't hate PHP. I just don't use it unless I have to.
but PHP is relatively modern, robust, and fully capable of handling enterprise tasks.
I'm not sure what you mean by "relatively modern". If you mean it is younger then Perl, that is true. 20 years old vs Perl's 26 years.
Both languages have evolved, adopting new ideas and adapting to new needs. They both borrow from other languages and from each other. Indeed PHP started out as a set of Perl scripts. A side effect of this was that PHP 1.0 (released in 1995) "syntax resembled that of Perl" (http://en.wikipedia.org/wiki/PHP).
Both are "fully capable of handling enterprise tasks".
The original posting claimed Perl "just seems to be ossifying". I think this is a perception problem unwittingly caused by the Perl 6 project. I think what we call Perl 5.20 might have been Perl 7.x (or even 8.x or higher) if the developers were free to increment the 5. As a similar example, look at FireFox and Chrome. Google's use of a single version number created a perception that FireFox 3.x was ancient. After Mozilla switched to using single number version for FireFox, the perception of FireFox began to improve. Another example: When Intel added "MMX extensions" to Pentium, people asked when will PowerPC get MMX extensions. The fact that the PowerPC already had equivalent features was ignored and the PowerPC was painted as falling behind the Pentium.
Perl, PHP and many other "old" languages are still used. If anything, their continued use is better evidence to expect they will be actively supported 5 (or more) years from now then whatever the current "rising star" happens to be..