只需循环遍历这些行，并将数量加到由dd值索引的不同数组中。

$in = array(array()); // your input
$out = array();
foreach ($in as $row) {
    if (!isset($out[$row['dd']])) {
        $out[$row['dd']] = array(
            'dd' => $row['dd'],
            'quantity' => 0,
        );
    }
    $out[$row['dd']]['quantity'] += $row['quantity'];
}
$out = array_values($out); // make the out array numerically indexed
var_dump($out);

因为日子是独一无二的：

<?php

  header('Content-type: text/plain');

  $inputArray  = array(
    array('qty' => 5,  'dd'  => '01-Nov-2012'),
    array('qty' => 10, 'dd'  => '01-Nov-2012'),
    array('qty' => 3,  'dd'  => '02-Nov-2012'),
    array('qty' => 4,  'dd'  => '03-Nov-2012'),
    array('qty' => 15, 'dd'  => '03-Nov-2012'));

  $outputArray = array();

  foreach ( $inputArray as $record ) {
    if ( !key_exists($record['dd'], $outputArray) ) {
      $outputArray[$record['dd']] = 0;
    }
    $outputArray[$record['dd']] += $record['qty'];
  }

  print_r($outputArray);

将产生：

Array
(
    [01-Nov-2012] => 15
    [02-Nov-2012] => 3
    [03-Nov-2012] => 19
)

有许多可行的技术可以对2d数组数据进行分组和求和。

1. foreach()和临时密钥：（Demo）

$result = [];
foreach ($array as $row) {
    if (!isset($result[$row['dd']])) {
        $result[$row['dd']] = $row;
    } else {
        $result[$row['dd']]['quantity'] += $row['quantity'];
    }
}
var_export(array_values($result));

1. foreach()使用引用而不是临时结果键：（Demo）

$result = [];
foreach ($array as $row) {
    if (!isset($ref[$row['dd']])) {
        $ref[$row['dd']] = $row;
        $result[] = &$ref[$row['dd']];
    } else {
        $ref[$row['dd']]['quantity'] += $row['quantity'];
    }
}
var_export($result);

1. array_reduce()和临时密钥：（Demo）

var_export(
    array_values(
        array_reduce(
            $array,
            function($result, $row) {
                if (!isset($result[$row['dd']])) {
                    $result[$row['dd']] = $row;
                } else {
                    $result[$row['dd']]['quantity'] += $row['quantity'];
                }
                return $result;
            }
        )
    )
 );

1. array_reduce()使用引用而不是临时键：（Demo）

var_export(
    array_reduce(
        $array,
        function($result, $row) {
            static $ref = [];
            if (!isset($ref[$row['dd']])) {
                $ref[$row['dd']] = $row;
                $result[] = &$ref[$row['dd']];
            } else {
                $ref[$row['dd']]['quantity'] += $row['quantity'];
            }
            return $result;
        }
    )
);

要对其他列值执行更多求和操作，请复制这些代码段的else分支中的求和操作。
例如：

} else {
    $result[$row['dd']]['quantity'] += $row['quantity'];
    $result[$row['dd']]['anotherColumn'] += $row['anotherColumn'];
    // ... and so on
}

要按多个列进行分组，请通过将多个列值连接到单个临时字符串键中来创建“复合键”。以下是该技术的一些演示：

• Group multidimensional array data based on two column values and sum values of one column in each group
• Group/Merge rows from two 2d arrays based on 3 identifying columns and fill missing column values with null
• Group rows of data, sum number of occurrences in each group, and print data as formatted strings
• Group data in a multidimensional array based on two columns
• Group rows of a multidimensional array and form comma-separated values within each group
• Group rows by two columns, filter grouped data to only keep the lowest value, and restructure associative rows
• Group rows of data, maintain a subarray of ids within the group, and only present the lowest id in each group as the first level key
• Group multidimensional array data based on two column values and sum values of one column in each group
• how to create a pivot array in php