Group array by date and set value as keys

Question

I have an array like this

 0 => 
array (size=3)
  'datetime_read' => '2017-07-16 20:45:08'
  'parameter_name' =>  'Rainfall Amount'
  'reading' => '0.00'

 1 => 
array (size=3)
  'datetime_read' =>  '2017-07-16 20:45:08'
  'parameter_name' =>  'Rainfall Intensity'
  'reading' =>  '0.0'

2 => 
array (size=3)
  'datetime_read' => '2017-07-16 20:45:08' 
  'parameter_name' => 'Air Pressure' 
  'reading' =>  '77.45'

and I need to group the data per date and get the values of parameter names and reading

 [0] => Array
        (
            'datetime_read' => '2017-07-16 20:45:08'
            'Rainfall Amount' => '0.00'
            'Rainfall Intensity' => '0.0'
            'Air Pressure' => '77.45'
        )

@Rasclatt yes i tried a loop but my solution makes a multi dimensional array. — ibyte, Jul 17 '17 at 09:32
[Pivot an array with a body-less foreach](https://stackoverflow.com/a/71807961/2943403) then call `sort()` because the first element is what you are sorting on anyhow. — mickmackusa, May 20 '22 at 12:19

score 0 · Answer 1 · answered Jul 17 '17 at 04:50

There are multiple ways to solve this problem. This is how I would solve it:

Look for the array with the max size and write a loop that goes till that max value
Initialize a new array outside the loop. This is going to be the final array
Each time you traverse the loop, check the dates of all these arrays. If the date already exists in the new array, then simply add these parameters. Otherwise, you'll have to add the date too in the array.

localheinz · Accepted Answer · 2017-07-17T13:57:30.040

Try this (assuming $input is your input):

$combined = array_reduce(
    $input,
    function (array $carry, array $item) {
        $datetimeRead = $item['datetime_read'];
        $parameterName = $item['parameter_name'];
        $reading = $item['reading'];

        $carry[$datetimeRead['datetime_read'] = $datetimeRead;
        $carry[$datetimeRead][$parameterName] = $reading;

        return $carry;
    },
    []
);

ksort($combined);

$data = array_values($combined);

For reference, see:

Got it! Thanks for the answer! I encounter an error just a missing ")" in the function clause. — ibyte, Jul 17 '17 at 09:23

Group array by date and set value as keys

2 Answers2