<?php
//seek alter the iterator's internal indice instead of the value that key() returns. 
//This is a big trap if combining with uasort/natsort function. 

$a = new ArrayObject([4,3,2,1]);
$it = $a->getIterator();
$it->natsort();   //The Iterator preserve the key while sorting the array 
$it->rewind();
$first = $it->key();   //The first element is  1 and it's key is 3
echo $first. PHP_EOL;  // 3

$it->next();
$second = $it->key();
echo $second. PHP_EOL; //2

$it->next();
$it->seek($first);             //Was intended to seek to element 1, key 3, indice 0
echo  $it->key() . PHP_EOL; //end up 0 because seek took parameter as indice instead of key. It seek to element indice 3, element 4 key 0.

var_dump($it);

/* Output: 
3
2
0
object(ArrayIterator)#2 (1) {
  ["storage":"ArrayIterator":private]=>
  object(ArrayObject)#1 (1) {
    ["storage":"ArrayObject":private]=>
    array(4) {
      [3]=>
      int(1)
      [2]=>
      int(2)
      [1]=>
      int(3)
      [0]=>
      int(4)
    }
  }
}
*/

<?php
// didn't see any code demos...here's one from an app I'm working on

$array = array('1' => 'one',
               '2' => 'two',
               '3' => 'three');

$arrayobject = new ArrayObject($array);
$iterator = $arrayobject->getIterator();

if($iterator->valid()){
    $iterator->seek(1);            // expected: two, output: two
    echo $iterator->current();    // two
}

?>