> Even if Node was 5x slower than PHP I would still go for Node because of its easy jQuery syntax

That "jQuery syntax" has nothing to do with the language itself. jQuery uses Sizzle[0], which is a CSS selector library for JavaScript. There are plenty of PHP libraries which provide CSS selectors, such as the Symfony CssSelector component[1].

[0] https://github.com/jquery/sizzle

[1] https://github.com/symfony/CssSelector