Docs for static closures

Hello, I'd stumbled upon a static closure in a piece of code and failed to find anything in PHP docs that would put it as nicely as the answer on Stack Overflow by Anthony Ferrara did: http://stackoverflow.com/a/23554571. The only place I found that mentioned static closures is http://php.net/manual/en/closure.bindto.php Is there a place that explains what a static closure is and how it works? Thanks, Alex.