The main problem with this approach, as someone who programs in PHP daily, is it pollutes the scope. That makes debugging much, much harder - you lose track of variables, and the current state of the program is complicated. IMO, if a value is a throwaway, like an intermediate, we shouldn't be able to use it. So method chaining or nesting function calls prevents them. Then, when we break after these functions, we can't see fake values. It also prevents someone in the future mutating the throwaway values. Someone could easily insert logic or a call that mutates something in the middle of this and breaks the chain.

One way this is prevented in PHP is just using functions. But then you have functions just for the sake of scope, which isn't really what they're for. That introduces other annoyances.