二维数组求和,,,针对键名数量不等的情况

求和数组:$data = array(  '0' => array      (          'id' => 1518,          'date' => 1495728000,          'type' => 61,          'content' => '{"2":2,"3":4,"4":6,"5":8}'      ),  '1' => array      (          'id' => 1519,          'date' => 1495641600,          'type' => 62,          'content' => '{"1":3,"3":5,"2":5,"6":6}'      ),  '2' => array      (          'id' => 1519,          'date' => 1495555200,          'type' => 63,          'content' => '{"7":219,"8":112,"9":268}'      ),  '3' => array      (          'id' => 1519,          'date' => 1495468800,          'type' => 64,          'content' => '{"14":219,"16":112,"23":268,"18":268}'      )      );/**求和函数*$n  求和天数*$data  求和数据*/function sum($n,$data){  $sum = $sum_tmp = array();  foreach ($data as $key => $val) {      // print_r($val);exit;      $content = json_decode($val['content'],true);      // print_r($content);exit;      if ((($key + 1) % $n) != 0) {          //非$n的倍数  一直累加          foreach($content as $k=>$v){            if(!isset($sum_tmp[$k])){              $sum_tmp[$k] = $v;            }else{              $sum_tmp[$k] += $v;            }          }          if (($key + 1) == count($data)) {              $sum[$val['date']]['date'] = date('Y-m-d',($val['date']+($n-1)*86400)).'---'.date('Y-m-d',$val['date']);              foreach($sum_tmp as $k=>$v){                  $sum[$val['date']][$k] = $v;              }          }      } elseif ((($key + 1) % $n) == 0) {          //$n的倍数 缝$n求和          foreach($content as $k=>$v){            if(!isset($sum_tmp[$k])){              $sum_tmp[$k] = $v;            }else{              $sum_tmp[$k] += $v;            }          }          $sum[$val['date']]['date'] = date('Y-m-d',($val['date']+($n-1)*86400)).'--'.date('Y-m-d',$val['date']);          foreach($sum_tmp as $k=>$v){              $sum[$val['date']][$k] = $v;          }          unset($sum_tmp);      }  }  return $sum;}print_r(sum(2,$data));    //注红色部分为解决求和数组之间单元数量不等的问题打印结果为:
Array(    [1495641600] => Array        (            [date] => 2017-05-26--2017-05-25            [2] => 7            [3] => 9            [4] => 6            [5] => 8            [1] => 3            [6] => 6        )    [1495468800] => Array        (            [date] => 2017-05-24--2017-05-23            [7] => 219            [8] => 112            [9] => 268            [14] => 219            [16] => 112            [23] => 268            [18] => 268        ))