对内部数组时间戳进行排序

Question

I have an array with multiple elements that looks like this:

  {
"name": "DR",
"data": [
  [
    "1508112000000",
    4
  ],
  [
    "1534204800000",
    1
  ]
],
"type": "areaspline"
},
{
    "name": "SIT",
    "data": [
      [
        "1508112000000",
        4
      ],
      [
        "1534204800000",
        1
      ],
      [
        "1506384000000",
        3
      ],
      [
        "1534204800000",
        1
      ],
      [
        "1531094400000",
        1
      ],
      [
        "1528502400000",
        1
      ]
    ],
    "type": "areaspline"
  },

This is the exact format I use to send data into high charts, however, the problem is that the chart breaks if the timestamps inside each environment (DR, SIT) are not in order.

How can I sort the 'data' inside each environment by timestamp?

This JSON is generated in PHP and sent through to JavaScript. So I would like to know how to sort the data inside either PHP or JavaScript.

Thanks.

Answer 1

This is actually rather trivial, once you know about the usort function. It allows you to define your own sorting function, so you can sort based on any factor of whatever the 2 objects it is passed.

Note that from your example json I had to add a set of square brackets around the whole thing to get PHP to parse it with json_decode .

<?php

// note I had to add square brackets to your
// demo json ....

$json='[{
"name": "DR",
"data": [
  [
    "1508112000000",
    4
  ],
  [
    "1534204800000",
    1
  ]
],
"type": "areaspline"
},
{
    "name": "SIT",
    "data": [
      [
        "1508112000000",
        4
      ],
      [
        "1534204800000",
        1
      ],
      [
        "1506384000000",
        3
      ],
      [
        "1534204800000",
        1
      ],
      [
        "1531094400000",
        1
      ],
      [
        "1528502400000",
        1
      ]
    ],
    "type": "areaspline"
  }]';

$json_obj_arr=json_decode($json,true);

print_r($json_obj_arr);
print("

");

// a function to handle the sorting itself
// usort will pass it an array(timestamp,datavalue) for both
// $a and $b so we compare the [0] element of each
function cmp($a, $b)
{
    if ($a[0] == $b[0]) {
        return 0;
    }
    return ($a[0] < $b[0]) ? -1 : 1;
}


// loop through the array, first is indexed
for($i=0;$i<count($json_obj_arr);$i++){
    // then each one of those contains an
    // associtive array with an element named ['data'] -
    // this is an indexed array that you want sorted
    // on the [0] element

    usort($json_obj_arr[$i]['data'],"cmp");
}

print_r($json_obj_arr);
print("

");
?>