+运营商在PHP数组？ [英] + operator for array in PHP?

问题描述

$test = array('hi');
$test += array('test','oh');
var_dump($test);

这是什么 + 意味着在PHP数组？

推荐答案

从 PHP手册上的语言报价操作符

+运算返回附加到左手阵列右手阵列;对于同时存在于两个阵列的键，从左侧数组中的元素将被使用，并且从右侧阵列的匹配元素将被忽略。

The + operator returns the right-hand array appended to the left-hand array; for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

所以，如果你

$array1 = ['one',   'two',          'foo' => 'bar'];
$array2 = ['three', 'four', 'five', 'foo' => 'baz']; 

print_r($array1 + $array2);

您将获得

Array
(
    [0] => one   // preserved from $array1 (left-hand array)
    [1] => two   // preserved from $array1 (left-hand array)
    [foo] => bar // preserved from $array1 (left-hand array)
    [2] => five  // added from $array2 (right-hand array)
)

所以逻辑 + 等同于下面的代码片段：

So the logic of + is equivalent to the following snippet:

$union = $array1;

foreach ($array2 as $key => $value) {
    if (false === array_key_exists($key, $union)) {
        $union[$key] = $value;
    }
}

如果您有兴趣在C级实现头的细节

If you are interested in the details of the C-level implementation head to

• http://lxr.php.net/xref/PHP_5_5/Zend/zend_operators.c#843

请注意，该 + 是如何不同 array_merge（） 将结合数组：

Note, that + is different from how array_merge() would combine the arrays:

print_r(array_merge($array1, $array2));

会给你

Array
(
    [0] => one   // preserved from $array1
    [1] => two   // preserved from $array1
    [foo] => baz // overwritten from $array2
    [2] => three // appended from $array2
    [3] => four  // appended from $array2
    [4] => five  // appended from $array2
)

请参阅链接的网页更多的例子。

See linked pages for more examples.

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