Question

That is variables that are visible to anonymous functions iside a main function. I ask because array_walk_recursive allow for only one additional parameter, it would be nice to be able to reach some vars from anonymous functions without relying on constant compact and extract

Answer 1

Closure can:

function() use ($var) { /*code*/}

Use use(vars) to close over these variables in your function.

Can’t post a link to the official use docu because php.net lacks there