工作遇到的PHP数组数据合并、排序问题

机械的增删改查做多了，脑子都转不动了，

今天遇到一个需要运用算法的问题，愣是研究了半天，特此记录：

下面开始我的表演：

根据一下数组中create_time字段求每天各个字段平均值

数组数据源如下：

$data=array(43) {
  [0] => array(8) {
    ["id"] => int(6)
    ["PM1"] => float(1)
    ["PM25"] => float(2)
    ["PM10"] => float(3)
    ["humidity"] => float(4)
    ["temperature"] => float(5)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-01-29"
  }
  [1] => array(8) {
    ["id"] => int(7)
    ["PM1"] => float(1.1)
    ["PM25"] => float(2)
    ["PM10"] => float(3.3)
    ["humidity"] => float(4.5)
    ["temperature"] => float(5.8)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-01-29"
  }
  [2] => array(8) {
    ["id"] => int(8)
    ["PM1"] => float(11)
    ["PM25"] => float(22)
    ["PM10"] => float(33)
    ["humidity"] => float(44)
    ["temperature"] => float(55)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-01"
  }
  [3] => array(8) {
    ["id"] => int(9)
    ["PM1"] => float(11)
    ["PM25"] => float(22)
    ["PM10"] => float(33)
    ["humidity"] => float(44)
    ["temperature"] => float(55)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-01"
  }
  [4] => array(8) {
    ["id"] => int(10)
    ["PM1"] => float(17)
    ["PM25"] => float(21)
    ["PM10"] => float(23)
    ["humidity"] => float(114)
    ["temperature"] => float(252)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-02"
  }
  [5] => array(8) {
    ["id"] => int(11)
    ["PM1"] => float(17)
    ["PM25"] => float(21)
    ["PM10"] => float(23)
    ["humidity"] => float(114)
    ["temperature"] => float(252)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-03"
  }
  
  [6] => array(8) {
    ["id"] => int(23)
    ["PM1"] => float(15)
    ["PM25"] => float(19)
    ["PM10"] => float(21)
    ["humidity"] => float(129)
    ["temperature"] => float(252)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-03"
  }
  [7] => array(8) {
    ["id"] => int(24)
    ["PM1"] => float(15)
    ["PM25"] => float(19)
    ["PM10"] => float(21)
    ["humidity"] => float(124)
    ["temperature"] => float(252)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-03"
  }
  [8] => array(8) {
    ["id"] => int(25)
    ["PM1"] => float(15)
    ["PM25"] => float(19)
    ["PM10"] => float(21)
    ["humidity"] => float(121)
    ["temperature"] => float(252)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-04"
  }
  [9] => array(8) {
    ["id"] => int(26)
    ["PM1"] => float(15)
    ["PM25"] => float(19)
    ["PM10"] => float(21)
    ["humidity"] => float(120)
    ["temperature"] => float(252)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-04"
  }
  [10] => array(8) {
    ["id"] => int(27)
    ["PM1"] => float(15)
    ["PM25"] => float(19)
    ["PM10"] => float(21)
    ["humidity"] => float(119)
    ["temperature"] => float(253)
    ["lid"] => int(1)
    ["create_time"] => string(10) "2018-02-04"
  }
}

首先把数组按create_time分组

public function group()
{
  $flag = $data[0]['create_time'];
  $new[$flag][] = $data[0];
  $len = count($data);
  for ($i=1;$i< $len; $i++){
      if ( $data[$i]['create_time'] == $flag ){
          $new[$flag][]= $data[$i];
      }else{
          $flag = $data[$i]['create_time'];
          $new[$flag][] = $data[$i];
      }
  }
  $data = self::getAvgData($new);
}

下一步，对每天的数据求平均值：

protected static function getAvgData($new)
{
    if (!is_array($new)){
        exit();
    }
    foreach ($new as $key => $value){
        $flag = $value[0];
        for ( $i = 1; $i < count($value); $i++ ){
            $flag['PM1'] = $flag['PM1']  + $value[$i]['PM1'];
            $flag['PM25'] = $flag['PM25'] + $value[$i]['PM25'];
            $flag['PM10'] = $flag['PM10'] + $value[$i]['PM10'];
            $flag['temperature'] =$flag['temperature'] + $value[$i]['temperature'];
            $flag['lid'] =$flag['lid'] + $value[$i]['lid'];
        }
        array_shift($flag);
        foreach ($flag as $k => $v){
            $flag[$k] = $v / count($value);
        }
        $rest[$key] = $flag;
    }
    //return $rest;
    print_r($rest);
}

大功告成：

array(3) {
  ["2018-01-29"] => array(7) {
    ["PM1"] => float(1.05)
    ["PM25"] => float(2)
    ["PM10"] => float(3.15)
    ["humidity"] => float(2)
    ["temperature"] => float(5.4)
    ["lid"] => int(1)
    ["create_time"] => int(1009)
  }
  ["2018-02-02"] => array(7) {
    ["PM1"] => float(15.466666666667)
    ["PM25"] => float(20.4)
    ["PM10"] => float(23.6)
    ["humidity"] => float(2.9333333333333)
    ["temperature"] => float(225.6)
    ["lid"] => int(1)
    ["create_time"] => float(134.53333333333)
  }
  ["2018-02-03"] => array(7) {
    ["PM1"] => float(15)
    ["PM25"] => float(19)
    ["PM10"] => float(21)
    ["humidity"] => float(4.9615384615385)
    ["temperature"] => float(252.53846153846)
    ["lid"] => int(1)
    ["create_time"] => float(77.615384615385)
  }
}