Getting an array key using the max() function

Question

I'm using the max() function to find the largest value in an array. I need a way to return the key of that value. I've tried playing with the array_keys() function, but all I can get that to do is return the largest key of the array. There has to be a way to do this but the php manuals don't mention anything.

Here's a sample of the code I'm using:

$arrCompare = array('CompareOne' => $intOne,
                    'CompareTwo' => $intTwo,
                    'CompareThree' => $intThree,
                    'CompareFour' => $intfour);

$returnThis = max($arrCompare);

I can successfully get the highest value of the array, I just can't get the associated key. Any ideas?

Edit: Just to clarify, using this will not work:

$max_key = max( array_keys( $array ) );

This compares the keys and does nothing with the values in the array.

It seems odd that `array_keys()` doesn't help you. – Dor Aug 15 '11 at 18:12 — Dor, Aug 15 '11 at 18:12
@Dor: Using `array_keys` compares the key values. – Evan Mulawski Aug 15 '11 at 18:13 — Evan Mulawski, Aug 15 '11 at 18:13

score 25 · Accepted Answer · answered Aug 15 '11 at 18:16

25

array_search function would help you.

$returnThis = array_search(max($arrCompare),$arrCompare);

answered Aug 15 '11 at 18:16

kravemir

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score 8 · Answer 2 · answered Jan 30 '15 at 06:16

8

If you need all keys for max value from the source array, you can do:

$keys = array_keys($array, max($array));

answered Jan 30 '15 at 06:16

Funcraft

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Prefer this one, though it's perhaps less obvious than `array_search()`. I didn't even know that `array_keys` could take a `$search_value` as its second argument! – Tom Auger Mar 16 '16 at 17:00
This returned the SECOND highest key. I went with this answer and that worked in my case : https://stackoverflow.com/questions/6126066/search-for-highest-key-index-in-an-array – Cagy79 Aug 14 '17 at 21:23

Evan Mulawski · Answer 3 · 2011-08-15T18:14:39.047

4

Not a one-liner, but it will perform the required task.

function max_key($array)
{
    $max = max($array);
    foreach ($array as $key => $val)
    {
        if ($val == $max) return $key;
    }
}

From http://cherryblossomweb.de/2010/09/26/getting-the-key-of-minimum-or-maximum-value-in-an-array-php/

edited Aug 15 '11 at 18:14

answered Aug 15 '11 at 18:09

Evan Mulawski

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Don't recalculate `max($array)` in each loop iteration - I very much doubt the PHP runtime is smart enough to hoist that out of the loop – Adam Wright Aug 15 '11 at 18:14
@Adam: Wow. Thanks a bunch. I can't believe I missed that when I was reading it! – Evan Mulawski Aug 15 '11 at 18:15
I tested this and it works but it is a bit verbose. I'm going to go with Miro's solution, but thank anyway. – Cloudkiller Aug 15 '11 at 18:26

Getting an array key using the max() function

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