Search for highest key/index in an array

Question

How can I get the highest key/index in an array with php? I know how to do it for the values.

E.g.: from this array I would like to get 10 as an integer value:

$arr = array(1 => "A", 10 => "B", 5 => "C");

I know how I could code it but I was asking myself if there is a function for this as well.

score 234 · Accepted Answer · answered May 25 '11 at 14:34

234

This should work fine

$arr = array( 1 => "A", 10 => "B", 5 => "C" );
max(array_keys($arr));

answered May 25 '11 at 14:34

Gérald Croës

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20

Do you know if it would work as well if one key is set like this: $arr = array( 1 => "A", 10 => "B", 5 => "C", "15" => "D"); – Raffael Luthiger May 25 '11 at 14:54
4

@Raffael Luthiger try testing it and see if you get the right results. – Jonathan Kuhn May 25 '11 at 15:01
2

This doesn't handle the case of an empty array. Straight from the PHP manual for `max`: ```If an empty array is passed, then FALSE will be returned and an E_WARNING error will be emitted.``` – Siphon Mar 20 '19 at 19:36
does not work for empty / 1 element array – j4r3k Sep 21 '21 at 14:25

score 35 · Answer 2 · answered May 25 '11 at 14:36

35

You can get the maximum key this way:

<?php
$arr = array("a"=>"test", "b"=>"ztest");
$max = max(array_keys($arr));
?>

answered May 25 '11 at 14:36

Fabrizio D'Ammassa

4,729
25
32

I'm sorry, someone posted the same answer before me. – Fabrizio D'Ammassa May 25 '11 at 14:37
does not work for empty / 1 element array – j4r3k Sep 21 '21 at 14:26

score 2 · Answer 3 · edited Jul 18 '21 at 07:22

I had a situation where I needed to obtain the next available key in an array, which is the highest + 1.

For example, if the array is $data = ['1' => 'something, '34' => 'something else'], then I needed to calculate 35 to add a new element to the array that had a key higher than any of the others. In the case of an empty array I needed 1 as next available key.

This is the solution that worked:

$highest = 0;
foreach ($data as $idx => $dummy) {
    if ($idx > $highest) $highest = $idx;
}
$highest++;

It will work in all cases, empty array or not. If you only need to find the highest key rather than highest key + 1, delete the last line.

You will then get a value of 0 if the array is empty.

score 1 · Answer 4 · answered May 25 '11 at 14:33

1

$keys = array_keys($arr);
$keys = rsort($keys);

print $keys[0];

should print "10"

answered May 25 '11 at 14:33

Cfreak

19,191
6
49
60

rsort always return true https://www.php.net/manual/en/function.rsort.php – j4r3k Sep 21 '21 at 14:31

j4r3k · Answer 5 · 2021-09-21T19:02:49.153

1

function getMaxKey(array $array): ?int
{
    if ($array === []) {
        return null;
    }

    return max(0, ...array_keys($array));
}

assuming you don't have negative keys like int -1

edited Sep 21 '21 at 19:02

answered Sep 21 '21 at 14:37

j4r3k

156
5

score 0 · Answer 6 · edited Jul 18 '21 at 07:19

0

Try max() function, see the first comment on that page.

edited Jul 18 '21 at 07:19

matiaslauriti

7,065
4
31
43

answered May 25 '11 at 14:33

AllisonC

2,973
4
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Will `max()` works if keys are date? – amir22 Dec 20 '22 at 07:12
@amir22 - not sure, post an example of your array or just try it – AllisonC Feb 04 '23 at 16:37
The question was related to the keys. The max function does not work with the keys, but with the values of arrays. – Thomas Krcal May 05 '23 at 06:12

score -3 · Answer 7 · answered Jul 17 '21 at 23:56

-3

$higestKey = 0;
foreach ($data as $key => $value) {
    if (strlen($key) > $higestKey) $higestKey = strlen($key);
}

answered Jul 17 '21 at 23:56

Umar Alfaruq

507
1
6
8

1

What has the length of key string to do with the highest key? This also assumes that keys are strings which also isn't true for the data shown in the question. – BDL Jul 19 '21 at 08:49

Search for highest key/index in an array

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