If the closure doesn't use $this (an instance of the current class) then it doesn't need to store a reference to it, which also skips the bookkeeping from the garbage collector.

In PHP, closures defined inside a class method automatically capture `$this`, which means the closure holds a reference to the entire object even if it never uses it. This prevents the object from being garbage collected and adds overhead. The optimization detects when `$this` isn't actually used and makes the closure static automatically, dropping that unnecessary reference.