pestaa's comment needs to be amended. It should read: "A sane engineer with a little bit of experience would not start off with PHP to build anything at all in 2013."

Facebook's former CTO has said that the only reason Facebook is still on PHP still today is legacy. It wouldn't be written in PHP if it were started today.

PHP once was the right tool for the job, but those years have passed. We have many better options now.