如何根據特定項目合併數組的行？

Question

我有一個這樣的數組：

$arr = [[1, "red"], 
     [2, "blue"], 
     [3, "yellow"], 
     [1, "green"], 
     [4, "green"], 
     [3, "red"]]; 

，這是預期的結果：

$output = [[1, ["red", "green"]], 
      [2, ["blue"]], 
      [3, ["yellow","red"]], 
      [4, ["green"]]]; 

就是幹這個可以通過PHP？

Answer 1

該結構不是很方便，考慮到你可以使用索引號作爲數組鍵，所以如果是我，我會堅持在我的答案是陣列$ temp創建的結構。總之，你想要的結果，你可以這樣做：

$arr = [[1, "red"], 
      [2, "blue"], 
      [3, "red"], 
      [1, "green"], 
      [4, "green"], 
      [2, "red"]]; 
    $res = array(); 
    $temp = array(); 
    $keys = array(); 
    foreach ($arr as $v) { 
     $temp[$v[0]][] = $v[1]; 
    } 
    foreach (array_keys($temp) as $k) { 
     $res[]=array($k,$temp[$k]); 
    } 

此外，您預期的結果，因爲該指數，看上去更像是：

$output = [[1, ["red", "green"]], 
      [2, ["blue","red"]], 
      [3, ["red"]], 
      [4, ["green"]]]; 

Answer 2

這可以通過減少轉換來完成，然後截斷鍵在通過array_values聲明建立所需的輸出之後。

//take only values (re-indexing 0..4) 
$output = array_values(
    //build associative array with the value being a 'tuple' 
    //containing the index and a list of values belonging to that index 
    array_reduce($arr, function ($carry, $item) { 

    //assign some names for clarity 
    $index = $item[0]; 
    $color = $item[1]; 

    if (!isset($carry[$index])) { 
     //build up empty tuple 
     $carry[$index] = [$index, []]; 
    } 

    //add the color 
    $carry[$index][1][] = $color; 

    return $carry; 

    }, []) 
); 

Answer 3

使用foreach環和array_values功能簡易的解決方案：

$arr = [[1, "red"], [2, "blue"], [3, "red"], [1, "green"], [4, "green"], [2, "red"]]; 

$result = []; 
foreach ($arr as $pair) { 
    list($k, $v) = $pair; 
    (isset($result[$k]))? $result[$k][1][] = $v : $result[$k] = [$k, [$v]]; 
} 
$result = array_values($result);