How to implement sorting and add rankings in PHP two-dimensional arrays?

Detailed explanation of PHP two-dimensional array sorting and ranking algorithm

This article will explain in detail how to efficiently sort PHP two-dimensional arrays and add ranking information to each subarray. In the example, the PHP two-dimensional array contains two fields "sequence number" (xuhao) and "vote number" (piaoshu). We will sort according to the number of votes in descending order (the number of votes is the same is preferred if the number of votes is small), and add a "paraming" field for each subarray.

The initial data structure is as follows:

 $data = array(
  array("xuhao" => "1", "piaoshu" => 3),
  array("xuhao" => "2", "piaoshu" => 5),
  array("xuhao" => "3", "piaoshu" => 5),
);

Our goal is to: arrange in descending order of piaoshu fields. When piaoshu values ​​are the same, arrange in ascending order of xuhao fields, and add paiming fields to each subarray to display the ranking.

The core function is array_multisort , which can sort multidimensional arrays. We first extract piaoshu and xuhao fields, sort them with array_multisort , and finally add the ranking to the original array.

The code implementation is as follows:

 $data = array(
  array("xuhao" => "1", "piaoshu" => 3),
  array("xuhao" => "2", "piaoshu" => 5),
  array("xuhao" => "3", "piaoshu" => 5),
);

$piaoshu = array_column($data, 'piaoshu');
$xuhao = array_column($data, 'xuhao');

array_multisort($piaoshu, SORT_DESC, $xuhao, SORT_ASC, $data);

$rank = 1;
$prev_piaoshu = -1;
foreach ($data as &$item) {
    if ($item['piaoshu'] != $prev_piaoshu) {
        $item['paiming'] = $rank;
        $prev_piaoshu = $item['piaoshu'];
        $rank ;
    } else {
        $item['paiming'] = $rank;
    }
}

print_r($data);

The code first extracts piaoshu and xuhao , and then uses array_multisort function to sort in descending order of votes and ascending order of numbers. Next, the code traverses the sorted array, calculates the ranking based on the number of votes, and adds it to each subarray. If the votes are the same, the ranking will increase.

Final result:

 array(3) {
  [0]=>
  array(3) {
    ["xuhao"]=>
    string(1) "2"
    ["piaoshu"]=>
    int(5)
    ["paiming"]=>
    int(1)
  }
  [1]=>
  array(3) {
    ["xuhao"]=>
    string(1) "3"
    ["piaoshu"]=>
    int(5)
    ["paiming"]=>
    int(2)
  }
  [2]=>
  array(3) {
    ["xuhao"]=>
    string(1) "1"
    ["piaoshu"]=>
    int(3)
    ["paiming"]=>
    int(3)
  }
}

This method efficiently completes the sorting and ranking of two-dimensional arrays.

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