Calculate the total in the tree structure data in PHP

Preface

In the process of project development, sometimes we encounter tree structure data calculation, which calculates the sum of all data values from the last level node to the root node , That is, calculate that the sum of the child node data is equal to the parent node , And so on to the root node .
The following method uses the recursive query calculation method .
Tree structure data example ：

$tree = [
    0 => [
        "Code" => "1",
        "PCode" => "",
        "num" => 1,
        "Price" => 2,
        "children" => [
            0 => [
                "Code" => "1.1",
                "PCode" => "1",
                "num" => 1,
                "Price" => 3,
            ],
            1 => [
                "Code" => "1.2",
                "PCode" => "1",
                "num" => 1,
                "Price" => 4,
            ],
        ],
    ],
    1 => [
        "Code" => "2",
        "PCode" => "",
        "num" => 1,
        "Price" => 2,
        "children" => [
            0 => [
                "Code" => "2.1",
                "PCode" => "2",
                "num" => 1,
                "Price" => 3,
            ],
            1 => [
                "Code" => "2.2",
                "PCode" => "2",
                "num" => 1,
                "Price" => 3,
                "children" => [
                    0 => [
                        "Code" => "2.2.1",
                        "PCode" => "2.2",
                        "num" => 1,
                        "Price" => 3,
                    ],
                ],
            ],
        ],
    ],
];

The total price of the node is calculated here = The unit price * Number

function sum($data)
{
    
    $aaa = 0;
    foreach ($data as $item) {
    
        if (isset($item['children']) && count($item['children']) > 0) {
    
            $item['TotalPrice'] = sum($item['children']); // total 
        } else {
    
            $item['TotalPrice'] = $item['num'] * $item['Price']; // Total price 
        }
        $aaa += $item['TotalPrice'];
    }
    return $aaa;
}

Call the method

$a = sum($tree);
print_r($a);// The total in the example data is 13