There was some legitimate criticism to be had about PHP 5.x being slow, especially if it wasn't paired with an opcode cache system / accelerator.
But in practice, the Node.js ecosystem is all built around evented I/O and PHP has to execute them one at a time.
(Well, actually with libraries like Kraken and ReactPHP and amp, you can have an event loop, but there are not that many I/O options for you.)
There was some legitimate criticism to be had about PHP 5.x being slow, especially if it wasn't paired with an opcode cache system / accelerator.