[humanrebar]

I guess this is a problem with trivial examples.

Pulling redundant work out of loops is a category of optimization that is widely used. In many cases, the optimizer can detect a lack of side effects on $list inside the loop body and perform the above optimization.

[esailija]

The canonical PHP implementation is a simple interpreter that cannot even dream of such optimizations. Hell, it uses unions to handle dynamic typing and hash tables to represent objects.

The implementation by facebook (HipHop) might have such an optimization though.