Search for highest key/index in an array

问题

How can I get with PHP the highest key/index in an array? 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 program it, but I was asking myself if there as a function for this as well.

回答1:

This should work fine

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

回答2:

You can get the maximum key this way:

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

回答3:

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

print $keys[0];

should print "10"

回答4:

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.

回答5:

Try max(): http://php.net/manual/en/function.max.php See the first comment on that page

来源：https://stackoverflow.com/questions/6126066/search-for-highest-key-index-in-an-array