我正在尝试弄清楚如何对具有相似日期的多维数组的某些值求和。

这是我的数组:

<?$myArray=array(

array(
        'year' => 2011,
        'month ' => 5,
        'day' => 13,
        'value' => 2
    ),
array(
        'year' => 2011,
        'month '=> 5,
        'day' => 14,
        'value' => 5
    ),
array(
        'year' => 2011,
        'month ' => 5,
        'day' => 13,
        'value' => 1
    ),
array(
        'year' => 2011,
        'month ' => 5,
        'day' => 14,
        'value' => 9
    )
);?>

这是我希望输出的样子:

<?$output=array(

array(
        'year' => 2011,
        'month ' => 5,
        'day' => 13,
        'value' => 3 //the sum of 1+2
    ),
array(
        'year' => 2011,
        'month '=> 5,
        'day' => 14,
        'value' => 14 //the sum of 5+9
    )
);?>

注意 4 个子数组是如何在 year/month/day 上匹配的，然后只对 value 求和。我见过其他 SO threads on this topic但找不到一个只对 value 求和而不对 year/month/day 值求和的地方。

想法？

最佳答案

最初使用年/月/日的组合索引输出数组可能是最简单的:

注意:上面的示例数组的所有 month 键都带有尾随空格。我只是在这里使用 month，没有尾随空格。

// Initialize output array...
$out = array();

// Looping over each input array item
foreach ($myArray as $elem) {
  // Initialize a new element in the output keyed as yyyy-mm-dd if it doesn't already exist
  if (!isset($out[$elem['year'] . "-" . $elem['month '] . "-" . $elem['day']])) {
    $out[$elem['year'] . "-" . $elem['month '] . "-" . $elem['day']] = array(
      // Set the date keys...
      'year' => $elem['year'],
      'month' => $elem['month '],
      'day' => $elem['day'],
      // With the current value...
      'value' => $elem['value']
    );
  }
  // If it already exists, just add the current value onto it...
  else {
     $out[$elem['year'] . "-" . $elem['month '] . "-" . $elem['day']]['value'] += $elem['value'];
  }
}

// Now your output array is keyed by date.  Use array_values() to strip off those keys if it matters:
$out = array_values($out);

输出(在调用 array_values() 之前):

array(2) {
  '2011-5-13' =>
  array(4) {
    'year' =>
    int(2011)
    'month' =>
    int(5)
    'day' =>
    int(13)
    'value' =>
    int(3)
  }
  '2011-5-14' =>
  array(4) {
    'year' =>
    int(2011)
    'month' =>
    int(5)
    'day' =>
    int(14)
    'value' =>
    int(14)
  }
}

更新:

要用单键日期(而不是 3 部分)做同样的事情，没有串联会更容易:

$myArray=array(
      array(
            'date' => '2011-05-13',
            'value' => 2
        ),
    array(
            'date' => '2011-05-14',
            'value' => 5
        ),
        array(
            'date' => '2011-05-13',
            'value' => 7
        ),
    array(
            'date' => '2011-05-14',
            'value' => 3
        ),

);

   foreach ($myArray as $elem) {
      // Initialize a new element in the output if it doesn't already exist
      if (!isset($out[$elem['date']])) {
        $out[$elem['date'] = array(
          // Set the date keys...
          'date' => $elem['date'],
          // With the current value...
          'value' => $elem['value']
        );
      }
      else {
        $out[$elem['date']]['value'] += $elem['value'];
      }
    }

关于PHP 数组 : summing values with matching dates，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12142144/