Question

关联数组：["Apple" => "Red", "Sun => "Red", "Grass" => "Green"]

更改为：["Red" => ["Apple", "Sun"], "Green" => ["Grassy"]]。

Answer 1

没有内置函数，但是只有一行代码可以为您完成。
循环数组并生成键值和值键

<button onclick="accept()">Accept Offer</button>
<button onclick="cancelAccept()">Cancel</button>

或

foreach($arr as $key => $val){
    $new[$val][] = $key;
}

var_dump($new);

返回

foreach($arr as $key => $val) $new[$val][] = $key;