PHP多维数组排序之array_multisort

在上一篇中我使用了usort这个函数来排序多维数组，以及根据数组里的2个字段来排序数组。然而PHP也提供了一个专门给多维数组排序的函数array_multisort,所以今天来学习一下这个函数也和usort比较一下具体的区别。

首先看一下这个函数的原型

bool array_multisort ( array &$array1 [, mixed $array1_sort_order = SORT_ASC [, mixed $array1_sort_flags = SORT_REGULAR [, mixed $... ]]] )

首先我们需要生成一个排序数组array1,然后给出一个排序规则比如SORT_ASC这个默认常量，与之对应的当然是SORT_DESC。
先简单看一下使用TotalPrice这个字段来对数组进行倒序排序

foreach ($hotelList as $key => $v) {
    $totalPrice[] = $v['TotalPrice'];
}
array_multisort($totalPrice, SORT_DESC, $hotelList); //默认SORT_ASC可以省略,而SORT_DESC不能省略

得到如下排序后的数组

array:7 [▼
  0 => array:4 [▼
    "LastId" => 32778
    "Time" => "2017-07-24T01:38:09+08:00"
    "OrderId" => 171868405
    "TotalPrice" => 700
  ]
  1 => array:4 [▼
    "LastId" => 32749
    "Time" => "2017-07-24T01:35:25+08:00"
    "OrderId" => 171868375
    "TotalPrice" => 400
  ]
  2 => array:4 [▼
    "LastId" => 32714
    "Time" => "2017-07-24T10:36:33+08:00"
    "OrderId" => 171868350
    "TotalPrice" => 200
  ]
  3 => array:4 [▼
    "LastId" => 32731
    "Time" => "2017-07-24T00:38:00+08:00"
    "OrderId" => 171868367
    "TotalPrice" => 200
  ]
  4 => array:4 [▼
    "LastId" => 32733
    "Time" => "2017-07-24T09:20:00+08:00"
    "OrderId" => 171868366
    "TotalPrice" => 200
  ]
  5 => array:4 [▼
    "LastId" => 32757
    "Time" => "2017-07-24T01:36:00+08:00"
    "OrderId" => 171868383
    "TotalPrice" => 160
  ]
  6 => array:4 [▼
    "LastId" => 32769
    "Time" => "2017-07-24T01:36:59+08:00"
    "OrderId" => 171868395
    "TotalPrice" => 150
  ]
]

可以看到，使用这个函数必须先拿到一个排序数组，比usort稍微繁琐一点。但是如果我们在PHP版本大于5.5以上可以这样来写，一步到位。

array_multisort(array_column($hotelList, 'TotalPrice'), SORT_ASC, $hotelList);

这个函数还有第三个flag参数，没怎么用到，不过也很好理解。只是项目里用默认的就可以，除非一些特殊情况。目前还没想到哪些场景要修改flag，所以这里也就不讨论了。接下来我们使用2个字段来同时对数组进行排序。

foreach ($hotelList as $key => $v) {
    $totalPrice[] = $v['TotalPrice'];
    $time[] = $v['Time'];
}
array_multisort($totalPrice, SORT_ASC, $time, SORT_DESC, $hotelList);

如果所有字段都是正序那么可以省略SORT_ASC参数，即

array_multisort($totalPrice, $time, $hotelList);

那么PHP5.5+的写法就很明白了，自己想吧。

结果如下

array:7 [▼
  0 => array:4 [▼
    "LastId" => 32769
    "Time" => "2017-07-24T01:36:59+08:00"
    "OrderId" => 171868395
    "TotalPrice" => 150
  ]
  1 => array:4 [▼
    "LastId" => 32757
    "Time" => "2017-07-24T01:36:00+08:00"
    "OrderId" => 171868383
    "TotalPrice" => 160
  ]
  2 => array:4 [▼
    "LastId" => 32714
    "Time" => "2017-07-24T10:36:33+08:00"
    "OrderId" => 171868350
    "TotalPrice" => 200
  ]
  3 => array:4 [▼
    "LastId" => 32733
    "Time" => "2017-07-24T09:20:00+08:00"
    "OrderId" => 171868366
    "TotalPrice" => 200
  ]
  4 => array:4 [▼
    "LastId" => 32731
    "Time" => "2017-07-24T00:38:00+08:00"
    "OrderId" => 171868367
    "TotalPrice" => 200
  ]
  5 => array:4 [▼
    "LastId" => 32749
    "Time" => "2017-07-24T01:35:25+08:00"
    "OrderId" => 171868375
    "TotalPrice" => 400
  ]
  6 => array:4 [▼
    "LastId" => 32778
    "Time" => "2017-07-24T01:38:09+08:00"
    "OrderId" => 171868405
    "TotalPrice" => 700
  ]
]

$incrOrderList = array_reduce($incrOrderList,
    function($rst, $v)  {
        $rst[$v['OrderId']] = $v;
        return $rst;
    }, array()
);
$incrOrderList = array_values($incrOrderList);//为了变成{[]}