从 PHP 中的多维数组中删除重复数组

Question

如何从这个数组中过滤重复值？

实际上，对于相同的country 和city，数据是相同的- 只是人口发生了变化。

如何删除包含较高人口的数组？

$arr = array
(
    "100" => array(
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '1800000',
        ),
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '2000000',
        ),
        array(
            "country" => 'France',
            "city" => 'Toulouse',
            "population" => '500000',
        ),
    )
    "101" => array(
        array(
            "country" => 'Russia',
            "city" => 'Moscow',
            "population" => '144000000',
        )
    )
);

所以期望的输出应该是：

$arr = array
(
    "100" => array(
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '1800000'
        ),
        array(
            "country" => 'France',
            "city" => 'Toulouse',
            "population" => '500000'
        ),
    )
    "101" => array(
        array(
            "country" => 'Russia',
            "city" => 'Moscow',
            "population" => '144000000',
        )
    )
);

这是我尝试过的：

$temp_array = [];
foreach ($array as &$v) {
    if (!isset($temp_array[$v['country']] && $temp_array[$v['city']]))
        $temp_array[$v[$key]] =& $v;
    }
$array = array_values($temp_array);
return $array;

Answer 1

您可以先使用array_reduce 过滤较低的人口（使用国家和城市的组合作为键）。然后分解它们并使用该最小值重置数组：

foreach($arr as $k => &$ar) {
    $temp = array_reduce($ar, function ($carry, $item) {
        $key = $item["country"] . "###" . $item["city"];
        $carry[$key] = (isset($carry[$key]) && $item["population"] > $carry[$key]) ?  $carry[$key] : $item["population"];
        return $carry;
    }, []);
    $ar = [];
    foreach($temp as $k => $val) {
        list($country, $city) = explode("###", $k);
        $ar[] = array("country" => $country, "city" => $city, "population" => $val);
    }
}

现场示例：3lv4

编辑：

您可以使用array_filter 代替foreach 循环来避免应对：

$ar = array_filter($ar, function ($item) use ($mins) {
    $key = $item["country"] . "###" . $item["city"];
    return $mins[$key] == $item["population"];
 });

Answer 2

从外观上看，数组已经按国家分组，我假设每个数组元素只有来自同一国家的子数组。我还要说，无论如何，为每个国家/地区提供一个包含密钥的数组更明智，以便于访问和过滤线路，所以我会说

$populations = [];

foreach($array as $arr) {
if(!isset($populations[$arr['country']])) $populations[$arr['country']] = [];//create an array entry for the country
     $cities = [];
     foreach($arr as $city) {
       if(!isset($cities[$city]) || $cities[$city]['population'] > $city['population']) $cities[$city] = ['population' => $city['population']];//you could put the value straight in, but this means if you expand later you could add extra fields to each cities info such as district, number of unemployed or whatever you're using this for

     }
$populations[$arr['country']] = $cities;
}

这与您概述的输出略有不同，但我认为它会使进一步使用变得更简单，因为您可以访问特定国家的所有数据，然后访问其中的城市，而不必不断循环并检查孩子是否包含您所追求的国家/地区。

我希望这是有道理的，我的未婚妻在我回答的同时试图和我谈论宜家，所以它可能不是 100% 完美，但至少会为你指明一个好的方向

Answer 3

我做了两个嵌套循环，第一个获取包含特定键（例如 100 和 101）的所有内容的子数组。

接下来我遍历数据，并保留一个具有两个级别的临时数组，第一个将国家作为键，第二个将作为跟踪人口最少的城市作为键。

完成上述操作后，我会遍历临时数组以获取正确格式的国家、城市和人口，并将其附加到新数组中。然后我用之前的数组替换这个新获得的结果。

<?php

$arr = array
(
    "100" => array(
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '1800000',
        ),
        array(
            "country" => 'France',
            "city" => 'Paris',
            "population" => '2000000',
        ),
        array(
            "country" => 'France',
            "city" => 'Toulouse',
            "population" => '500000',
        ),
    ),
    "101" => array(
        array(
            "country" => 'Russia',
            "city" => 'Moscow',
            "population" => '144000000',
        )
    )
);

foreach($arr as $key=>$subarr) {
    $tmp = array();
    foreach($subarr as $v) {
        $country = $v['country'];
        $city = $v['city'];
        $population = $v['population'];

        if(isset($tmp[$country])) {
            if(isset($tmp[$country][$city])) {
                if($tmp[$country][$city] > $population) {
                    $tmp[$country][$city] = $population;
                }
            } else {
                $tmp[$country][$city] = $population;
            }
        } else {
            $tmp[$country] = array();
            $tmp[$country][$city] = $population;
        }
    }

    $res = array();
        foreach($tmp as $country=>$cities) {
            foreach($cities as $city=>$population) {
                $res[] = array('country'=>$country,'city'=>$city,'population'=>$population);
            }
        }
    $arr[$key] = $res;

}
print_r($arr);

Answer 4

您可以使用国家和城市创建一个复合数组键，这样可以轻松跟踪您循环的内容。
由于城市可能不在数组中，所以如果它需要不得到通知。

foreach($arr as $key => $sub){
    foreach($sub as $item){
        if(isset($item['city'])){
            if(!isset($res[$key][$item['country'] . $item['city']])) $res[$key][$item['country'] . $item['city']] = $item;
            if($res[$key][$item['country'] . $item['city']] < $item['population']) $res[$key][$item['country'] . $item['city']] = $item;
        }else{
            if(!isset($res[$key][$item['country']])) $res[$key][$item['country']] = $item;
            if($res[$key][$item['country']] < $item['population']) $res[$key][$item['country']] = $item;
        }
    }
}
var_dump($res);

输出：

array(2) {
  [100]=>
  array(2) {
    ["FranceParis"]=>
    array(3) {
      ["country"]=>
      string(6) "France"
      ["city"]=>
      string(5) "Paris"
      ["population"]=>
      string(7) "1800000"
    }
    ["FranceToulouse"]=>
    array(3) {
      ["country"]=>
      string(6) "France"
      ["city"]=>
      string(8) "Toulouse"
      ["population"]=>
      string(6) "500000"
    }
  }
  [101]=>
  array(1) {
    ["Russia"]=>
    array(2) {
      ["country"]=>
      string(6) "Russia"
      ["population"]=>
      string(9) "144000000"
    }
  }
}

https://3v4l.org/KNuId

如果您需要删除“FranceToulouse”等键，则只需再次循环数组并使用 array_values