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Bug #39811 array_diff "compare with 2" bug
Submitted: 2006-12-13 07:49 UTC Modified: 2006-12-13 11:32 UTC
From: wishm at bk dot ru Assigned:
Status: Not a bug Package: Arrays related
PHP Version: 4.4.4 OS: win32
Private report: No CVE-ID: None
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 [2006-12-13 07:49 UTC] wishm at bk dot ru 
Description:
------------
array_diff() function fails on comparing any array element with 2, when another pair of elements are both set to 2. Fails with that settings only.

Reproduce code:
---------------
<?php
$a = array("2","2");
$b = array("2","any_symbols_here");
// same thing on $b = array("any_symbols_here","2");
print_r(array_diff($a,$b));
?>

Expected result:
----------------
Array ( [1] => 2 ) 

// second elements are not equal so function should return that element from $a array

Actual result:
--------------
Array ( )

//empty array - function failed

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 [2006-12-13 10:06 UTC] tony2001@php.net 
http://php.net/array_diff

array_diff() returns an array containing **all the values of array1 that are not present in any of the other arguments*.

In your case all values of $a are present in $b.
 [2006-12-13 11:10 UTC] wishm at bk dot ru 
I think you dont understand the purpose of the array_diff() function. The element is considered present if and only if its' VALUE is equal to the same-named element's VALUE in the second array! Try array_diff(array("a"=>"1"),array("a"=>"2")). The element a = 1 does not present at second array so it will be returned. You didnt even tried to understand the essence of the bug! It is 100% PHP error when 2 is considered equal to ANY value under conditions I've described. Please fix that!
 [2006-12-13 11:27 UTC] tony2001@php.net 
>I think you dont understand the purpose of the array_diff() function.

And I think you didn't read what I said and keep ignoring the docs.

>The element is considered present if and only if its'
>VALUE is equal to the same-named element's VALUE in the
>second array!

No. Read the documentation first.
http://php.net/array_diff
 [2006-12-13 11:29 UTC] tony2001@php.net 
There is even Russian translation of this particular page:
http://ru.php.net/manual/ru/function.array-diff.php
 [2006-12-13 11:29 UTC] wishm at bk dot ru 
ok the problem was just at this function's "feature" - multiple occurrences in first array are all treated the same way. I was wondered that applies to the associative arrays, too. So indexes are simply ignored. Screwed up a bit... array_diff_assoc fixes that :) Sorry for the bothering.
 [2006-12-13 11:32 UTC] tony2001@php.net 
.
 
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