php - + PHP中数组的运算符？

Question

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

+对于PHP中的数组是什么意思？

Answer 1

引自 PHP Manual on Language Operators

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.

如果你这样做了

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

print_r($array1 + $array2);

你会得到

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+的逻辑等价于如下代码段:

$union = $array1;

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

如果您对 C 级实现的细节感兴趣，请前往

• php-src/Zend/zend_operators.c

---

注意，+ 与 array_merge() 不同。将组合数组:

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
)

查看链接页面了解更多示例。