所以我有两个数组如下：
$arr1 = array("apple","banana","lemon");
$arr2 = array("apple"=>4,"banana"=>1,"lemon"=>1);
我使用array_fill_keys来填充上面的数组：
$arr3 = array_fill_keys($arr1,1);
$arr4 = array_fill_keys($arr2,1);
当我为上面的4个数组执行array_sum时：
echo "Sum of Array1 is " . array_sum($arr1) . "\n";
echo "Sum of Array2 is " . array_sum($arr2) . "\n";
echo "Sum of Array3 is " . array_sum($arr3) . "\n";
echo "Sum of Array4 is " . array_sum($arr4) . "\n";
结果将是：
Sum of Array1 is 0
Sum of Array2 is 6
Sum of Array3 is 3
Sum of Array4 is 2
为什么Array4返回2而不是3？
答案 0 :(得分：1)
让我们在这里简化一下你的数组
$arr1 = array("apple","banana","lemon");
$arr2 = array("apple"=>4,"banana"=>1,"lemon"=>1);
//$arr3 = array_fill_keys($arr1,1);
$arr3 = array("apple"=>1,"banana"=>1,"lemon"=>1);
//$arr4 = array_fill_keys($arr2,1);
$arr4 = array(1=>1, 4=>1);
正如您所见，数组＃4（$ arr4）使用array_fill_keys添加了这些键
array( 4, 1, 1 );
这些是$ arr2的值，您的输入值是
1
产生这个数组
array(
4=>1,
1=>1,
1=>1
);
现在你可能知道php数组键是唯一的，所以第一个（1）键被第二个（1）键覆盖，导致这个
$arr4 = array_sum(array(1=>1, 4=>1));
http://php.net/manual/en/function.array-fill-keys.php
因此总和为2
答案 1 :(得分：0)
原因是因为<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
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</ul>将使用值4,1和1以及键并将其值设置为1.
array_fill_keys将成为
$arr2 = array("apple" => 4, "banana" => 1, "lemon"=> 1);
两个键为1将取消，因此数组中只剩下两个值。然后，PHP将使用提供的值替换所有值，即一个。
您的最终数组将如下所示
$arr2 = array(4 => "apple", 1 => "banana", 1 => "lemon");
$arr2 = array(4 => 1, 1 => 1);
，在数组中添加值，即array_sum。
答案 2 :(得分：0)
array_fill_keys（）被赋予一个键数组，并使用这些键和定义的值生成一个新数组。 $ arr2包含两个相同的值＆＃34; 1＆＃34;这意味着当你使用它来生成$ arr4时，只会创建两个值。
如果您需要使用第一个数组中的键，您应该考虑使用array_keys来使用键，而不是值：
$keys1 = array_keys($arr1);
$keys2 = array_keys($arr2);
$arr3 = array_fill_keys($keys1, 1);
$arr4 = array_fill_keys($keys2, 1);
这样（arr1和arr3）和（arr2和arr4）的键将匹配。
享受。