writes "Recently, Facebook provided us some information on their server park. They use about 30000 servers, and not surprisingly, most of them are running the PHP code to generate pages full of social info for their users. As they only say that "the bulk" is running PHP, let’s assume this to be 25 000 of the 30 000. If C++ would have been used instead of PHP, then 22 500 servers could be powered down (assuming a conservative ratio of 10 for the efficiency of C++ versus PHP code), or a reduction of 49 000 ton. Of course, it is a bit unfair to isolate Facebook here. Their servers are only a tiny fraction of computers deployed world-wide that are interpreting PHP code.
But I think it is fair to say that using PHP, especially for large deployments, is not very Kopenhagen."Link to Original Source