key

(PHP 4, PHP 5, PHP 7)

Fetch a key from an array

mixed key ( array &$array )

key() returns the index element of the current array position.

Parameters:

array

The array.

Returns:

The key() function simply returns the key of the array element that's currently being pointed to by the internal pointer. It does not move the pointer in any way. If the internal pointer points beyond the end of the elements list or the array is empty, key() returns NULL.

Examples:

key() example

<?php
$array = array(
    'fruit1' => 'apple',
    'fruit2' => 'orange',
    'fruit3' => 'grape',
    'fruit4' => 'apple',
    'fruit5' => 'apple');

// this cycle echoes all associative array
// key where value equals "apple"
while ($fruit_name = current($array)) {
    if ($fruit_name == 'apple') {
        echo key($array).'<br />';
    }
    next($array);
}
?>

The above example will output:

fruit1<br />
fruit4<br />
fruit5<br />