Gets the current key

# AppendIterator::key

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

AppendIterator::key — Gets the current key

### Description

public function 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

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