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Doc Bug #69059 array_udiff logical bug
Submitted: 2015-02-16 01:03 UTC Modified: 2015-03-01 04:22 UTC
From: geoleu11 at gmail dot com Assigned:
Status: No Feedback Package: *General Issues
PHP Version: Irrelevant OS: Ubuntu
Private report: No CVE-ID: None
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 [2015-02-16 01:03 UTC] geoleu11 at gmail dot com 
Description:
------------
---
From manual page: http://www.php.net/function.array-udiff
---

Since the information that can be selected for providing php version information, here is some info about the build : PHP Version 5.5.9-1ubuntu4.5 .

Also regarding the problem/bug source : array function, more specifically : array_udiff .

The output of the below script is : 

array (size=1)
  0 => string 'red' (length=3)  

Why does array_udiff return a common element from those arrays? Shouldn't it return the elements are present in the first array and not in the other arrays?

At least if you try internal array_diff, it does return the proper value from those 2 arrays below .

Test script:
---------------
$a1 = array('red');
$a2 = array('red', 'blue');

$diff = array_udiff($a1, $a2,
        function($a, $b) {
            if($a === $b) {
                return 0;
            }
            else {
                return -1;
            }
        });

var_dump($diff);

Expected result:
----------------
The expected result should be an empty array.

array (size=0)
  empty  

Actual result:
--------------
array (size=1)
  0 => string 'red' (length=3)

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 [2015-02-16 03:38 UTC] laruence@php.net
-Status: Open +Status: Feedback
 [2015-02-16 03:38 UTC] laruence@php.net 
compare function should return value greater than 0 if $a > $b, less than 0 if $b < $a.

thus, your codes should be:

<?php
$a1 = array('red');
$a2 = array('red', 'blue');

$diff = array_udiff($a1, $a2,
    function($a, $b) {
        if($a === $b) {
            return 0;
        }
        else {
            return $a > $b? 1 : -1;
        }
    });

var_dump($diff);


anyway, this bug doesn't exists in master because new sort algo impelemented.

thanks
 [2015-02-16 03:38 UTC] laruence@php.net 
s ,bug,issue,
 [2015-02-16 15:33 UTC] geoleu11 at gmail dot com 
Yes, I saw that if you return unsigned integer the sort/looping is different. That is why I said there is a logical bug. The result should be the same no matter if you use unsigned/signed negative integer. It should be a simple comparison : are those 2 values equal or unequal. This is a good way to properly compare array of objects. I ended up using a php made version of array_udiff.
Is 'red' > || < 'blue'? It's not about counting the bits, it's simply about checking for equality.

Having a logic/scenario for 3 type of returns seems prone to bugs (at least in my case was). That is why array_udiff should treat negative int and unsigned int the same. So basically one scenario for 0 and one for negative/unsigned int.

If there is a fix relating to this function in the current php dev version, a documentation update would be nice that explains how negative int is treated compared to a unsinged int for the callback function.

Thanks
 [2015-03-01 04:22 UTC] php-bugs at lists dot php dot net 
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
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change the status of the bug back to "Re-Opened". Thank you.
 
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