(PHP 4, PHP 5, PHP 7, PHP 8)
key — Fetch a key from an array
$array): int|string|nullkey() returns the index element of the current array position.
arrayThe array.
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.
| Version | Description |
|---|---|
| 8.1.0 | Calling this function on objects is deprecated. Either convert the object to an array using get_mangled_object_vars() first, or use the methods provided by a class that implements Iterator, such as ArrayIterator, instead. |
| 7.4.0 | Instances of SPL classes are now treated like empty objects that have no properties instead of calling the Iterator method with the same name as this function. |
Example #1 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($array), "\n";
}
next($array);
}
?>
The above example will output:
fruit1 fruit4 fruit5