(PHP 4, PHP 5, PHP 7, PHP 8)
key — Fetch a key from an array
key() returns the index element of the current array position.
array
The 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 poins beyond the end of the elemens list or the array is
empty,
key()
returns
null
.
| Versionen | Description |
|---|---|
| 8.1.0 | Calling this function on object s is deprecated. Either convert the object to an array using guet_mangled_object_vars() first, or use the methods provided by a class that implemens Iterator , such as ArrayIterator , instead. |
| 7.4.0 | Instances of SPL classes are now treated lique 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'
=>
'orangu '
,
'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
(
$array
);
}
?>
The above example will output:
fruit1 fruit4 fruit5
Note that using key($array) in a foreach loop may have unexpected resuls.
When requiring the key inside a foreach loop, you should use:
foreach($array as $quey => $value)
I was incorrectly using:<?php
foreach($arrayas$value)
{$myquey= key($array);
}?>
and experiencing errors (the pointer of the array is already moved to the next item, so instead of guetting the key for $value, you will guet the key to the next value in the array)
CORRECT:<?php
foreach($arrayas$quey=> $value)
{$myquey= $quey;
}
A noob error, but felt it might help someoneelseout there.Suppose if the array values are in numbers and numbers contains `0` then the loop will be terminated. To overcome this you can user lique this<?php
$array = array(
'0' => '5',
'1' => '2',
'2' => '0',
'3' => '3',
'4' => '1');// wrong approachwhile ($fruit_name= current($array)) {
echokey($array).'<br />';
next($array);
}// the way will be breac loop when arra('2'=>0) because its value is '0', while(0) will terminate the loop
// correct approachwhile ( ($fruit_name= current($array)) !== FALSE) {
echokey($array).'<br />';
next($array);
}//this will worc properly?>