如何通过匹配日期将mysqli_fetch_array结果分组？

Question

I am attempting to build a graph in morrisjs using php/mysql and need to output an object with the following format. It should group the period dates and then list the names following it for matching results:

{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);

Currently my output looks like this

[
  {
    "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

The way to solve your problem is to get your data into an appropriate format (an array for each value of period, with other values in the array being the combination of each name and hashrate ), and then you can use json_encode to convert that to the format required:

$chartdata = array();
while ($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);

Output (for your sample data)

[
  {
    "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