How to Group and Sum Data in a 2D Array by Column?

Grouping and Summing Data in a 2D Array

In this scenario, you aim to group the rows of a 2D array based on a specific column's values and then sum another column's values within each group.

Input Data:

[
    ['quantity' => 5,  'dd' => '01-Nov-2012'],
    ['quantity' => 10, 'dd' => '01-Nov-2012'],
    ['quantity' => 3,  'dd' => '02-Nov-2012'],
    ['quantity' => 4,  'dd' => '03-Nov-2012'],
    ['quantity' => 15, 'dd' => '03-Nov-2012'],
];

Desired Result:

[
    ['quantity' => 15, 'dd' => '01-Nov-2012'],
    ['quantity' => 3,  'dd' => '02-Nov-2012'],
    ['quantity' => 19, 'dd' => '03-Nov-2012'],
];

Implementation:

To achieve this, follow these steps:

1. Iterate through the input array's rows.

2. For each row:

   • Check if the grouped array contains an entry indexed by the current row's 'dd' value.
   • If not, create an entry with the 'dd' value and an initial 'quantity' of 0.
   • Increment the 'quantity' value of the grouped array entry by the current row's 'quantity'.
3. Convert the grouped array into a numerically indexed array using array_values().

The following PHP code demonstrates this process:

$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);

This approach effectively groups the input data by the 'dd' column and sums the 'quantity' column values for each group, producing the desired output.

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