这是一个有趣的挑战。我有一系列子阵列，格式如下：
array
(
a => array ( id = 20, name = chimpanzee )
b => array ( id = 40, name = meeting )
c => array ( id = 20, name = dynasty )
d => array ( id = 50, name = chocolate )
e => array ( id = 10, name = bananas )
f => array ( id = 50, name = fantasy )
g => array ( id = 50, name = football )
)
我想根据每个子数组中的id字段将其分组到一个新数组中。
array
(
10 => array
(
e => array ( id = 10, name = bananas )
)
20 => array
(
a => array ( id = 20, name = chimpanzee )
c => array ( id = 20, name = dynasty )
)
40 => array
(
b => array ( id = 40, name = meeting )
)
50 => array
(
d => array ( id = 50, name = chocolate )
f => array ( id = 50, name = fantasy )
g => array ( id = 50, name = football )
)
)
谢谢！
答案 0 :(得分：89)
$arr = array();
foreach ($old_arr as $key => $item) {
$arr[$item['id']][$key] = $item;
}
ksort($arr, SORT_NUMERIC);
答案 1 :(得分：7)
foreach($array as $key => $value){
$newarray[$value['id']][$key] = $value;
}
var_dump($newarray);
小菜一碟;）
答案 2 :(得分：4)
如果其中一个内部数组不包含 id ，以下代码会调整@Tim Cooper的代码以缓解Undefined index: id错误：
$arr = array();
foreach($old_arr as $key => $item)
{
if(array_key_exists('id', $item))
$arr[$item['id']][$key] = $item;
}
ksort($arr, SORT_NUMERIC);
但是，它会丢弃没有id的内部数组。
E.g。
$old_arr = array(
'a' => array ( 'id' => 20, 'name' => 'chimpanzee' ),
'b' => array ( 'id' => 40, 'name' => 'meeting' ),
'c' => array ( 'id' => 20, 'name' => 'dynasty' ),
'd' => array ( 'id' => 50, 'name' => 'chocolate' ),
'e' => array ( 'id' => 10, 'name' => 'bananas' ),
'f' => array ( 'id' => 50, 'name' => 'fantasy' ),
'g' => array ( 'id' => 50, 'name' => 'football' ),
'h' => array ( 'name' => 'bob' )
);
将完全删除'h'数组。
答案 3 :(得分：1)
<?php
$array = array(
'a' => array ( 'id' => 20, 'names' => 'chimpanzee' ),
'b' => array ( 'id' => 40, 'name' => 'meeting' ),
'c' => array ( 'id' => 20, 'name' => 'dynasty' ),
'd' => array ( 'id' => 50, 'name' => 'chocolate' ),
'e' => array ( 'id' => 10, 'name' => 'bananas' ),
'f' => array ( 'id' => 50, 'name' => 'fantasy' ),
'g' => array ( 'id' => 50, 'name' => 'football' )
);
$result = array();
foreach($array as $key => $value){
$id = $value['id'];
if(!isset($result[$id])) $result[$id] = array();
$result[$id] = array($key => $value);
}
var_dump($result);
?>
答案 4 :(得分：1)
您还可以使用Arrays::gorupBy表单ouzo-goodies：
$groupBy = Arrays::groupBy($array, Functions::extract()->id);
print_r($groupBy);
结果：
Array
(
[20] => Array
(
[0] => Array
(
[id] => 20
[name] => chimpanzee
)
[1] => Array
(
[id] => 20
[name] => dynasty
)
)
[40] => Array
(
[0] => Array
(
[id] => 40
[name] => meeting
)
)
[50] => Array
(
[0] => Array
(
[id] => 50
[name] => chocolate
)
[1] => Array
(
[id] => 50
[name] => fantasy
)
[2] => Array
(
[id] => 50
[name] => football
)
)
[10] => Array
(
[0] => Array
(
[id] => 10
[name] => bananas
)
)
)
答案 5 :(得分：1)
这是一个将数组作为第一个参数，将条件（字符串或回调函数）作为第二个参数的函数。该函数返回一个新数组，该数组按要求对数组进行分组。
/**
* Group items from an array together by some criteria or value.
*
* @param $arr array The array to group items from
* @param $criteria string|callable The key to group by or a function the returns a key to group by.
* @return array
*
*/
function groupBy($arr, $criteria): array
{
return array_reduce($arr, function($accumulator, $item) use ($criteria) {
$key = (is_callable($criteria)) ? $criteria($item) : $item[$criteria];
if (!array_key_exists($key, $accumulator)) {
$accumulator[$key] = [];
}
array_push($accumulator[$key], $item);
return $accumulator;
}, []);
}
这是给定的数组：
$arr = array(
'a' => array ( 'id' => 20, 'name' => 'chimpanzee' ),
'b' => array ( 'id' => 40, 'name' => 'meeting' ),
'c' => array ( 'id' => 20, 'name' => 'dynasty' ),
'd' => array ( 'id' => 50, 'name' => 'chocolate' ),
'e' => array ( 'id' => 10, 'name' => 'bananas' ),
'f' => array ( 'id' => 50, 'name' => 'fantasy' ),
'g' => array ( 'id' => 50, 'name' => 'football' )
);
以及使用带有字符串和回调函数的函数的示例：
$q = groupBy($arr, 'id');
print_r($q);
$r = groupBy($arr, function($item) {
return $item['id'];
});
print_r($r);
两个示例的结果相同：
Array
(
[20] => Array
(
[0] => Array
(
[id] => 20
[name] => chimpanzee
)
[1] => Array
(
[id] => 20
[name] => dynasty
)
)
[40] => Array
(
[0] => Array
(
[id] => 40
[name] => meeting
)
)
[50] => Array
(
[0] => Array
(
[id] => 50
[name] => chocolate
)
[1] => Array
(
[id] => 50
[name] => fantasy
)
[2] => Array
(
[id] => 50
[name] => football
)
)
[10] => Array
(
[0] => Array
(
[id] => 10
[name] => bananas
)
)
)
在上面的示例中，传递回调是多余的，但是当您传递对象数组，多维数组或要分组的任意对象时，使用回调会发现其用途。