PHP | CachingIterator key() Function

The CachingIterator::key() function is an inbuilt function in PHP which is used to return the key for the current element.

Syntax:

scalar CachingIterator::key( void )

Parameters: This function does not accept any parameters.

Return Value: This function returns the key value of the current element.

Below programs illustrate the CachingIterator::key() function in PHP:

Program 1:

<?php

// Declare an array
$arr = array('G', 'e', 'e', 'k', 's');

// Create a new CachingIterator
$cachIt = new CachingIterator(
    new ArrayIterator($arr),
    CachingIterator::FULL_CACHE
);

foreach($cachIt as $element) {
    echo $cachIt->key() . "\n";
}

?>

Output:

0
1
2
3
4

Program 2:

<?php

// Declare an ArrayIterator
$arr = array(
    "a" => "Geeks",
    "b" => "for",
    "c" => "Geeks",
    "d" => "Computer",
    "e" => "Science",
    "f" => "Portal"
);

// Create a new CachingIterator
$cachIt = new CachingIterator(
    new ArrayIterator($arr),
    CachingIterator::FULL_CACHE
);

foreach($cachIt as $element) {
    echo "key: " . $cachIt->key() . "  Value: "
            . $cachIt->current() . "\n";
}

?>

Output:

key: a  Value: Geeks
key: b  Value: for
key: c  Value: Geeks
key: d  Value: Computer
key: e  Value: Science
key: f  Value: Portal

Reference: https://www.php.net/manual/en/cachingiterator.key.php