iterator_to_array

One important thing to remember is that in iterator can be infinite. Not all iterators necessarily end. If iterator_to_array is used on such an iterator, it will exhaust the available memory, and throw a fatal error.For example, consider the following code:<?phpfunction fibonacci(): Generator{    yield $a = 1;    yield $b = 2;    start:    yield $c = $a + $b;    $a = $b;    $b = $c;    goto start;}$fibonacciSequence = fibonacci();iterator_to_array($fibonacciSequence);?>Since <?php fibonacci(); ?> generates an infinite fibonacci sequence, which is valid, since it is actually an infinite sequence, then attempting to convert it to an array will fail.

Using the boolean param :

<?php

$first = new ArrayIterator( array('k1' => 'a' , 'k2' => 'b',  'k3' => 'c',  'k4' => 'd') );
$second = new ArrayIterator( array( 'k1' => 'X', 'k2' => 'Y', 'Z' ) );

$combinedIterator= new AppendIterator();
$combinedIterator->append( $first );
$combinedIterator->append( $second );

var_dump( iterator_to_array($combinedIterator, false) );

?>

will output : 

array(7) (
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
  [3]=>
  string(1) "d"
  [4]=>
  string(1) "X"
  [5]=>
  string(1) "Y"
  [6]=>
  string(1) "Z"
)

<?php

var_dump( iterator_to_array($combinedIterator, true) );

?>

will output (since keys would merge) :

array(5) (
  ["k1"]=>
  string(1) "X"
  ["k2"]=>
  string(1) "Y"
  ["k3"]=>
  string(1) "c"
  ["k4"]=>
  string(1) "d"
  [0]=>
  string(1) "Z"
)

To generate an deep array from nested iterators:<?phpfunction iterator_to_array_deep(\Traversable $iterator, $use_keys = true) {    $array = array();    foreach ($iterator as $key => $value) {        if ($value instanceof \Iterator) {            $value = iterator_to_array_deep($value, $use_keys);        }        if ($use_keys) {            $array[$key] = $value;        } else {            $array[] = $value;        }    }    return $array;}?>I use it to test an iterator: https://gist.github.com/jm42/cb328106f393eeb28751

When using iterator_to_array() on an SplObjectStorage object, it's advisable to set $use_keys to false.The resulting array is identical, since the iterator keys produced by SplObjectStorage::key() are always integers from 0 to (COUNT-1). Passing $use_keys=false cuts out the unnecessary calls to SplObjectStorage::key(), giving a slight performance advantage.