Worrying _too_ much about language efficiency when it comes to web programming is clearly a case of premature optimisation.
Well, sometimes it's a question of a choice between upgrading your hardware and optimizing your code (or even re-writing in some other language). Which is cheaper? I'm into it right now, haven't decided yet ;)
I worked with Perl before PHP but never grew to like it (it's not consistent enough and not exactly easy on the eyes, either).
I do understand the tradeoff between efficiency and power, and PHP hits that sweet spot just right for web programming.
Worrying _too_ much about language efficiency when it comes to web programming is clearly a case of premature optimisation. PHP is efficient enough (probably Perl and Python as well, maybe not Ruby ?).