Get key of object php

(PHP 4, PHP 5, PHP 7, PHP 8)

key — Fetch a key from an array

Description

key(array|object $array): int|string|null

Parameters

The array.

Return Values

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

Example #1 key() example

$array = array(
    'fruit1' => 'apple',
    'fruit2' => 'orange',
    'fruit3' => 'grape',
    'fruit4' => 'apple',
    'fruit5' => 'apple');// this cycle echoes all associative array
// key where value equals "apple"
while ($fruit_name = current($array)) {
    if ($fruit_name == 'apple') {
        echo key($array), "\n";
    }
    next($array);
}
?>

The above example will output:

See Also

• current() - Return the current element in an array
• next() - Advance the internal pointer of an array
• array_key_first() - Gets the first key of an array
• foreach

lhardie ¶

8 years ago

Note that using key($array) in a foreach loop may have unexpected results. 

When requiring the key inside a foreach loop, you should use:
foreach($array as $key => $value)

I was incorrectly using:
foreach($array as $value)
{
  $mykey = key($array);
}
?>

and experiencing errors (the pointer of the array is already moved to the next item, so instead of getting the key for $value, you will get the key to the next value in the array)

CORRECT:
foreach($array as $key => $value)
{
  $mykey = $key;
}A noob error, but felt it might help someone else out there.

vinob44 at gmail dot com ¶

8 years ago

Suppose if the array values are in numbers and numbers contains `0` then the loop will be terminated. To overcome this you can user like this

$array = array(
    '0' => '5',
    '1' => '2',
    '2' => '0',
    '3' => '3',
    '4' => '1');// wrong approachwhile ($fruit_name = current($array)) {

        echo

FatBat ¶

10 years ago

Needed to get the index of the max/highest value in an assoc array.
max() only returned the value, no index, so I did this instead.

reset($x);   // optional.
arsort($x);
$key_of_max = key($x);   // returns the index.
?>

Md Tahazzot ¶

2 years ago

(Editor note: Or just use the array_keys function)

Make as simple as possible but not simpler like this one :)

$k = array();
for($i = 0; $i < count($arr); $i++){
    $k[$i] = key($arr);
    next($arr);
}

danielmadsv at gmail dot com ¶

3 years ago

In addition to FatBat's response, if you'd like to find out the highest key in an array (assoc or not) but don't want to arsort() it, take a look at this:

$arr