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.

Transposition

Answer 1

This should work fine

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

Waterfall

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"); – Transposition

@Raffael Luthiger try testing it and see if you get the right results. – Sparrow

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. – Radiotelephone

does not work for empty / 1 element array – Hautevienne

Answer 2

You can get the maximum key this way:

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

Secretory

I'm sorry, someone posted the same answer before me. – Devise

does not work for empty / 1 element array – Hautevienne

Answer 3

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.

Ductile

Answer 4

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

print $keys[0];

should print "10"

Heilbronn

rsort always return true php.net/manual/en/function.rsort.php – Hautevienne

Answer 5

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

Hautevienne

Answer 6

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

Saveloy

Will max() works if keys are date? – Truncated

@Truncated - not sure, post an example of your array or just try it – Saveloy

The question was related to the keys. The max function does not work with the keys, but with the values ​​of arrays. – Solemnize

Answer 7

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

Cherrylchersonese

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. – Tarim