final public function walk(callable $callback)
    {
        $callback($this);

        foreach ($this->getChildren() as $child) {
            $child->walk($callback);
        }
    }
final public function walk(callable $callback)
    {
        $callback($this);

        foreach ($this->getChildren() as $child) {
            $child->walk($callback);
        }
    }
final public function walk ( callable $ callback ) { $ callback ( $ this ) ; foreach ( $ this -> getChildren ( ) as $ child ) { $ child -> walk ( $ callback ) ; } }
Walks the current expression and the children expressions.

@param callable $callback

@return void
Walks the current expression and the children expressions .