PHP MultipleIterator::rewind() Method: Usage and Examples

MultipleIterator combines values from multiple iterators at matching iteration positions.

What Is MultipleIterator::rewind in PHP?

Restarts traversal when supported by the wrapped iterator.

MultipleIterator::rewind()

This operation does not accept method arguments.

Example 1: Understanding the Basic Behavior

<?php

$iterator = new MultipleIterator(MultipleIterator::MIT_NEED_ANY);
$firstIterator = new ArrayIterator([1, 2]);
$secondIterator = new ArrayIterator(['a', 'b']);
$iterator->attachIterator($firstIterator, "numbers");
$iterator->attachIterator($secondIterator, "letters");
$iterator->rewind();
var_dump($iterator->current());

Output:

array(2) {
  [0]=>
  int(1)
  [1]=>
  string(1) "a"
}

Explanation: Restarts traversal when supported by the wrapped iterator.

Example 2: Testing Another Case

<?php

$iterator = new MultipleIterator(MultipleIterator::MIT_NEED_ANY);
$firstIterator = new ArrayIterator([5, 6]);
$secondIterator = new ArrayIterator(['c', 'd']);
$iterator->attachIterator($firstIterator, "numbers");
$iterator->attachIterator($secondIterator, "letters");
$iterator->rewind();
var_dump($iterator->current());

Output:

array(2) {
  [0]=>
  int(5)
  [1]=>
  string(1) "c"
}

Explanation: Rewinding is not supported equally by every Traversable source, especially consumed generators.

Practical Example: Applying the Operation

<?php

$iterator = new MultipleIterator(MultipleIterator::MIT_NEED_ANY);
$firstIterator = new ArrayIterator([8, 9]);
$secondIterator = new ArrayIterator(['e', 'f']);
$iterator->attachIterator($firstIterator, "numbers");
$iterator->attachIterator($secondIterator, "letters");
$iterator->rewind();
var_dump($iterator->current());

Output:

array(2) {
  [0]=>
  int(8)
  [1]=>
  string(1) "e"
}

Explanation: The MIT_NEED_ALL and MIT_NEED_ANY options change when iteration stops; keys may be positional or associated.

Important Behavior and Edge Cases

• Rewinding is not supported equally by every Traversable source, especially consumed generators.
• The MIT_NEED_ALL and MIT_NEED_ANY options change when iteration stops; keys may be positional or associated.

Comparison With Related Approaches

Common Beginner Mistakes

Key Takeaways

• Restarts traversal when supported by the wrapped iterator.
• Rewinding is not supported equally by every Traversable source, especially consumed generators.
• The MIT_NEED_ALL and MIT_NEED_ANY options change when iteration stops; keys may be positional or associated.

The examples demonstrate where MultipleIterator::rewind fits within synchronized iteration. Verify the relevant preconditions whenever you adapt the code to real data.