如何按匹配日期对mysqli_fetch_array结果进行分组？

Question

我正在尝试使用php/mysql在morrisjs中构建一个图形，并需要输出以下格式的对象。它应该对期间日期进行分组，然后列出它后面的名称以获得匹配结果：

{period: "2019-02-06 12:00:00", shelly: 2147483647, debra: 1240996571, sally: 2147483647, bill: 2147483647, bob: 619685085, jim: 126614618},
{period: "2019-02-06 12:30:00", shelly: 2147483647, debra: 1240996571, sally: 2147483647, bill: 2147483647, bob: 619685085, jim: 126614618},
{period: "2019-02-06 13:00:00", shelly: 2147483647, debra: 1240996571, sally: 2147483647, bill: 2147483647, bob: 619685085, jim: 126614618}

PHP：

    while ($row = mysqli_fetch_array($poolChart)) {
        $chart_data .= "{ \"period\": \"".$row["StatsHistoryTime"]."\", \"name\": \"".$row["name"]."\", \"hashrate\":".$row["hashrate"]."}, ";

    }
    $chart_data = substr($chart_data, 0, -2);

目前，我的输出如下所示

[
  {
    "period": "2019-02-06 12:00:00",
    "name": "shelly",
    "hashrate": 2147483647
  },
  {
    "period": "2019-02-06 12:00:00",
    "name": "debra",
    "hashrate": 1240996571
  },
  {
    "period": "2019-02-06 12:00:00",
    "name": "sally",
    "hashrate": 2147483647
  },
  {
    "period": "2019-02-06 12:00:00",
    "name": "bill",
    "hashrate": 2147483647
  }
  {
    "period": "2019-02-06 12:30:00",
    "name": "shelly",
    "hashrate": 2147483647
  },
  {
    "period": "2019-02-06 12:30:00",
    "name": "debra",
    "hashrate": 1460613388
  },
  {
    "period": "2019-02-06 12:30:00",
    "name": "sally",
    "hashrate": 2147483647
  },
  {
    "period": "2019-02-06 12:30:00",
    "name": "bill",
    "hashrate": 2147483647
  }
]

Answer 1

解决问题的方法是将数据转换为适当的格式(周期的每个值对应一个数组，数组中的其他值是每个name和hashrate的组合)，然后可以使用json_encode将其转换为所需的格式：

$chartdata = array();
while ($row = mysqli_fetch_array($poolChart)) {
    $period = $row['StatsHistoryTime'];
    // have we already got data for this period?
    if (($k = array_search($period, array_column($chartdata, 'period'))) !== false) {
        // yes, update data for this period
        $chartdata[$k][$row['name']] = $row['hashrate'];
    }
    else {
        // no, create a new array
        $chartdata[] = array('period' => $period, $row['name'] => $row['hashrate']);
    }
}
echo json_encode($chartdata);

输出(用于示例数据)

[
  {
    "period":"2019-02-06 12:00:00",
    "shelly":2147483647,
    "debra":1240996571,
    "sally":2147483647,
    "bill":2147483647
  },
  {
    "period":"2019-02-06 12:30:00",
    "shelly":2147483647,
    "debra":1460613388,
    "sally":2147483647,
    "bill":2147483647
  }
]

Demo on 3v4l.org