Why must I rewind IteratorIterator

Question

$arrayIter = new ArrayIterator( array(1, 2) );
$iterIter = new IteratorIterator($arrayIter);

var_dump($iterIter->valid()); //false
var_dump($arrayIter->valid(         


        

Answer 1

With a fresh iterator the position isn't initialized, simply for performance reason, you can stack iterators on top of other iterators, if all of them would rewind during construction there would be some performance impact, additionally some iterators might change their first value after the constructor was executed - which is unknown to iterators further out.

Iterators are usually executed by foreach() which does a rewind() first ...