三维数组合并为二维数组并求出某个字段的总和

//  把对象转换为数组

public  function object2array(&$object) {
    $object =  json_decode( json_encode( $object),true);
    return  $object;
}

$array=3维数组；

foreach ($array as $key => $val) {
    foreach ($val['gift'] as $key2 => $val2) {
        $newhello[$k]['id'] = $val2['id'];
        $newhello[$k]['gift_name'] = $val2['gift_name'];
        $newhello[$k]['num'] = $val2['num'];
        $newhello[$k]['sum'] = $val2['sum'];
        $k++;
    }
}

print_r($newhello);

计算所有num的总和

$sum = 0;
foreach ($newhello as $key => $val) {
    $sum += $val['num'];
}

echo  $sum;