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php 使用 array_reduce 实现多维数组分组（groupby）聚合
在处理关联数组时，经常需要对多维数组按指定字段分组聚合，下面封装了一个数组分组聚合方法：
/** * 对数组进行分组聚合 * @param $array * @param $keys * @return $result */ function array_group_by($array, $keys) { if(!is_array($keys) || count($keys) == 1) { $key = is_array($keys) ? array_shift($keys) : $keys;
return array_reduce($array, function($tmp_result, $item) use ($key) { $tmp_result[$item[$key]][] = $item;
return $tmp_result; }); } else { $keys = array_values($keys);
$result = array_group_by($array, array_shift($keys));
foreach ($result as $k=>$value) { $result[$k] = array_group_by($value, $keys); }
return $result; } }
测试
$arr = [ [ "first" => "aa", "second" => "ccc", "third" => "sdfgg", ], [ "first" => "aa", "second" => "ccc", "third" => "dddsa", ], [ "first" => "aa", "second" => "sdfsdfd", "third" => "sdfgg", ], [ "first" => "bb", "second" => "ccc", "third" => "sdfgg", ], [ "first" => "bb", "second" => "sdfsdfd", "third" => "sdfgg", ], ]; print_r(array_group_by($arr, ['first'])); /* [ "aa" => [ [ "first" => "aa", "second" => "ccc", "third" => "sdfgg", ], [ "first" => "aa", "second" => "ccc", "third" => "dddsa", ], [ "first" => "aa", "second" => "sdfsdfd", "third" => "sdfgg", ], ], "bb" => [ [ "first" => "bb", "second" => "ccc", "third" => "sdfgg", ], [ "first" => "bb", "second" => "sdfsdfd", "third" => "sdfgg", ], ], ] */ print_r(array_group_by($arr, ['first','second'])); /* [ "aa" => [ "ccc" => [ [ "first" => "aa", "second" => "ccc", "third" => "sdfgg", ], [ "first" => "aa", "second" => "ccc", "third" => "dddsa", ], ], "sdfsdfd" => [ [ "first" => "aa", "second" => "sdfsdfd", "third" => "sdfgg", ], ], ], "bb" => [ "ccc" => [ [ "first" => "bb", "second" => "ccc", "third" => "sdfgg", ], ], "sdfsdfd" => [ [ "first" => "bb", "second" => "sdfsdfd", "third" => "sdfgg", ], ], ], ]
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