在数组中搜索最高键/索引

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

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


print $keys[0];

should print "10"

This should work fine

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

You can get the maximum key this way:

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

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.

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

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