# AppendIterator::key

(PHP 5 >= 5.1.0, PHP 7)

AppendIterator::key — Gets the current key

### Description

public AppendIterator::key ( ) : scalar

Get the current key.

### Parameters

This function has no parameters.

### Return Values

The current key if it is valid or `NULL` otherwise.

### Examples

Example #1 AppendIterator::key() basic example

`<?php
$array_a = new ArrayIterator(array('a' => 'aardwolf', 'b' => 'bear', 'c' => 'capybara'));
$array_b = new ArrayIterator(array('apple', 'orange', 'lemon'));
$iterator = new AppendIterator;
$iterator->append($array_a);
$iterator->append($array_b);
// Manual iteration
$iterator->rewind();
while ($iterator->valid()) {
echo $iterator->key() . ' ' . $iterator->current() . PHP_EOL;
$iterator->next();
}
echo PHP_EOL;
// With foreach
foreach ($iterator as $key => $current) {
echo $key . ' ' . $current . PHP_EOL;
}
?>`

The above example will output:

    a aardwolf
    b bear
    c capybara
    0 apple
    1 orange
    2 lemon

    a aardwolf
    b bear
    c capybara
    0 apple
    1 orange
    2 lemon

### See Also

- Iterator::key() - Return the key of the current element
- AppendIterator::current() - Gets the current value
- AppendIterator::valid() - Checks validity of the current element
- AppendIterator::next() - Moves to the next element
- AppendIterator::rewind() - Rewinds the Iterator