array_udiff似乎不起作用 [英] array_udiff seems not work

问题描述

我正在尝试将两个数组与array_udiff进行比较，但这很奇怪.看来array_udiff无法得到正确的答案.这是实时演示.结果应该是一个空数组，但不过滤掉一个元素.

I'm trying to compare two array with array_udiff, but it's very weired. it seems array_udiff not get the right answer. Here is the live demo. The result should be an empty array, but leave one element unfiltered out.

<?php

$string = '{
  "sakiniai": [

      {
        "Faktas": "A",
        "value": "true"
      },
      {
        "Faktas": "B",
        "value": "true"
      },
      {
        "Faktas": "A",
        "value": "false"
      }
  ]
}';

$sakiniais = json_decode($string, true)['sakiniai'];


$v = $sakiniais[0];
$arr[] = $v;
$v['value'] = $v['value'] == "true" ? "false" : "true";
$arr[] = $v;
var_dump($arr);
var_dump($sakiniais);


print_r(array_udiff($arr, $sakiniais, function($a, $b){
/*
var_dump($a);
var_dump($b);
var_dump($a == $b);
echo "\n\n\n";
*/
return $a == $b ? 0 : -1;}
));

输出

    array(2) {
  [0]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
  }
  [1]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
  }
}
array(3) {
  [0]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
  }
  [1]=>
  array(2) {
    ["Faktas"]=>
    string(1) "B"
    ["value"]=>
    string(4) "true"
  }
  [2]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
  }
}
Array
(
    [1] => Array
        (
            [Faktas] => A
            [value] => false
        )

)

推荐答案

问题是array_udiff并未在所有值之间进行比较，这似乎是由您的compare函数引起的.

The problem is that array_udiff is not performing the comparison between all values, and this seems to be caused by your compare function.

array_udiff()期望可调用函数是一个真正的比较函数，但是您始终返回0和-1，但永远不会返回1.

array_udiff() expects that the callable function is a real compare function, but you are returning always 0 and -1, but never 1.

在执行其工作之前，array_udiff()尝试对两个数组进行排序并也删除重复项.如果它不能依靠您的比较功能，那么它就无法执行所有需要的比较，并且某些值会跳变".

Before doing its job, array_udiff() tries to order both arrays and remove duplicates too. If it can't rely on your comparison function, it can't perform all the needed comparison and some values are "jumped".

查看文档中的所有注释特别是napcoder注释

Look at all comments in the documentation expecially napcoder comment

请注意，比较功能也可在内部使用，以便对 数组，然后选择在下一轮中与哪个元素进行比较.

Note that the compare function is used also internally, to order the arrays and choose which element compare against in the next round.

如果您的比较函数未真正进行比较(即，如果返回，则返回0 元素等于，否则为1)，您将收到意外的信息 结果.

If your compare function is not really comparing (ie. returns 0 if elements are equals, 1 otherwise), you will receive an unexpected result.

这是对您的阵列的演示

$ arr

array(2) {
  [0]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
  }
  [1]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
  }
}

和$ sakiniais

and $sakiniais

array(3) {
  [0]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
  }
  [1]=>
  array(2) {
    ["Faktas"]=>
    string(1) "B"
    ["value"]=>
    string(4) "true"
  }
  [2]=>
  array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
  }
}

您应该期望要测试的两个数组之间的所有组合，但是被测试的组合(如下所示)不包括A-False vs. A-False

You should expect all the combinations between the two arrays to be tested, but the tested combinations (below) doesn't include A-False vs. A-False

array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
}
array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
}
bool(false)



array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
}
array(2) {
    ["Faktas"]=>
    string(1) "B"
    ["value"]=>
    string(4) "true"
}
bool(false)



array(2) {
    ["Faktas"]=>
    string(1) "B"
    ["value"]=>
    string(4) "true"
}
array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
}
bool(false)



array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
}
array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
}
bool(true)



array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(4) "true"
}
array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
}
bool(false)



array(2) {
    ["Faktas"]=>
    string(1) "A"
    ["value"]=>
    string(5) "false"
}
array(2) {
    ["Faktas"]=>
    string(1) "B"
    ["value"]=>
    string(4) "true"
}
bool(false)

在本文的正确答案中，还有一些其他有用的见解关于array_udiff的工作原理

In the correct answer at this post there are some other useful insights on how array_udiff works

您可以这样更改退货声明

You can change your return statement like this

if ($a < $b) {
    return -1;
} elseif ($a > $b) {
    return 1;
} else {
    return 0;
}

(如果您想知道如何比较两个数组的大/小，请查看

(if you are wondering how two arrays can be compared for less/greater, have a look at this link, in the section "Comparison with Various Types" and the "Example #2 Transcription of standard array comparison" example)

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