PHP：如何通过键更新关联数组中的值

Question

我在尝试更新数组中的值时遇到了困难。我制作了一个简单的示例来说明这一点：数组包含球员的姓名和他们拥有的积分数量。每轮比赛后，我想像这样更新他们的积分：

(但这并没有起作用)

 $players = array (
   array (
   "id"        => 0, 
   "name"      => "John",
   "points"    => 0
   ),

   array (
   "id"        => 1, 
   "name"      => "Chris",
   "points"    => 0
   ),

   array (
   "id"        => 2, 
   "name"      => "Peter",
   "points"    => 0
   ),

   array (
   "id"        => 3, 
   "name"      => "Greg",
   "points"    => 0
   ),

 );


 $points0 = 10;
 $points1 = 20;
 $points2 = 30;
 $points3 = 40;


 $i = 0;
 foreach ($players as $player) {
        if ($player["id"] == $i) { 
         $player["points"] = ${"points".$i}; 
     }    $i++;
 }

 var_dump($players);

可能很愚蠢，但我已经尝试了几个小时，但我就是找不到。

感谢您的帮助！

- Roddeh

---

你调试过你的代码了吗？查看压缩和赋值运算符之间的区别。 - hassan

在这里你正在进行比较，想要赋值的话，我相信应该是 $player["points"] = ${"points".$i};。编辑提示：首先。 - Funk Forty Niner

你可能想要使用一个数组来存储分数。例如：$points[0] = 10;$points[1]=20;等等。然后，你可以使用foreach($players as $player){ $player['points'] = $points[$player['id']]; }来为每个玩家分配对应的分数。 - Matt

@Fred-ii- 在这种情况下，周围的 {} 表示什么（变量）？我能以某种方式读取它吗？ - Antonios Tsimourtos

@AntonisTsimourtos 变量 可变变量 http://php.net/manual/zh/language.variables.variable.php - Funk Forty Niner

是的，抱歉，当然应该是 $player["points"] = ${"points".$i}; 也不起作用... - Roddeh

Answer 1

您需要向 $player 添加一个引用:

$players = array (
  array (
   "id"        => 0,
   "name"      => "John",
   "points"    => 0
   ),

   array (
   "id"        => 1,
   "name"      => "Chris",
   "points"    => 0
   ),

   array (
   "id"        => 2,
   "name"      => "Peter",
   "points"    => 0
   ),

   array (
   "id"        => 3,
   "name"      => "Greg",
   "points"    => 0
   ),

);


$points0 = 10;
$points1 = 20;
$points2 = 30;
$points3 = 40;


$i = 0;
foreach ($players as &$player) {
  if ($player["id"] == $i) {
    $player["points"] = ${"points".$i};
  }
  $i++;
}

重要的部分是 foreach 语句中的与号 &。如果没有它，您将无法记录对数组的任何更改。

- glaux

---

该死...为什么会这样？我不明白。谢谢！ - Roddeh

@Roddeh：PHP中的数组是按值传递还是按引用传递？ - Jay Blanchard

完美解决方案 - Vishal Baraiya

Answer 2

看起来你想使用循环来实现这个功能。如果是这样的话，你可以考虑将$points变量更改为数组类型，如下面的代码所示：

<?php


    $players = array (
        array (
            "id"        => 0,
            "name"      => "John",
            "points"    => 0
        ),

        array (
            "id"        => 1,
            "name"      => "Chris",
            "points"    => 0
        ),

        array (
            "id"        => 2,
            "name"      => "Peter",
            "points"    => 0
        ),

        array (
            "id"        => 3,
            "name"      => "Greg",
            "points"    => 0
        ),

    );

    // IF YOU INTEND TO ASSIGN THE VALUES USING A LOOP, IT IS SUGGESTED TO
    // RATHER MAKE $points AN ARRAY WITH EACH KEY CORRESPONDING TO THE KEY OF THE
    // MULTIDIMENSIONAL ARRAY $players AND THE VALUE BEING THE POINT TO BE ASSIGNED
    // TO THE SUB-ARRAY WITH THAT KEY LIKE SO:
    $points = [
      0   => 10,//IMPLIES: TARGET $players[0] & ADD 10 TO ITS points ITEM: "John"
      1   => 20,//IMPLIES: TARGET $players[1] & ADD 20 TO ITS points ITEM: "Chris"
      2   => 30,//IMPLIES: TARGET $players[2] & ADD 30 TO ITS points ITEM: "Peter"
      3   => 40,//IMPLIES: TARGET $players[3] & ADD 40 TO ITS points ITEM: "Greg"
    ];

    // NOW LOOP THROUGH THE $players MULTIDIMENSIONAL ARRAY...
    // AS YOU ITERATE THROUGH IT, TRY TO OBTAIN THE POINTS FROM THE $points ARRAY
    // USING THE LOOP INDEX ($key)....
    // IT IS ALSO IMPORTANT TO WORK WITH EACH PLAYER BY REFERENCE
    // USING THE & OPERATOR
    foreach ($players as $key=>&$player) {  // NOTICE THE &$player here
        $currentPlayersPoints   = $points[$key];
        // HAVING OBTAINED THE CURRENT PLAYER'S POINTS,
        // SIMPLY ADD THE VALUE TO THE THE ORIGINAL points ELEMENT
        $player['points'] += (int)$currentPlayersPoints;
    }

    // CHECK OUT YOUR RESULT::
    var_dump($players);

    // YIELDS:  
    array (size=4)
      0 => 
        array (size=3)
          'id'      => int 0
          'name'    => string 'John' (length=4)
          'points'  => int 10
      1 => 
        array (size=3)
          'id'      => int 1
          'name'    => string 'Chris' (length=5)
          'points'  => int 20
      2 => 
        array (size=3)
          'id'      => int 2
          'name'    => string 'Peter' (length=5)
          'points'  => int 30
      3 => 
        array (size=3)
          'id'      => int 3
          'name'    => string 'Greg' (length=4)
          'points'  => int 40

- Poiz