Question

Ok, I have a JSON string:

[{
"Name": "Title 1",
"Count1": 556,
"Count2": 5,
"Date": "2012-12-05"
}, {
"Name": "Title 2",
"Count1": 10,
"Count2": 100,
"Date": "2012-12-05"
}, {
"Name": "Title 3",
"Count1": 798,
"Count2": 11,
"Date": "2012-12-04"
}...

and I run json_decode on that, get an array, and now I want to run through that array and calculate totals for Count1 and Count2 for each date… (and the dates can go on for whatever range). What’s the fastest/niftiest way of doing that?

Sort of loop through each key => val par in a foreach, and then somehow group the date keys into a new key in a new array and add the totals in there, so that I’m getting this as an output, in JSON feed at the very end, after json_encode, sorted by date:

[{
"Date": "2012-12-05"
"TotalCount1": 566,
"TotalCount2": 105,
}, {
"Date": "2012-12-04"
"TotalCount1": 798,
"TotalCount2": 11,
}...

how would I group the array values like that before sending the whole array to json_encode?

Answer 1

I think using a $totals array indexed on your date would work here (if I understand you correctly). Something like the example below where $data is your decoded associative JSON array:

$totals = array();

foreach ($data as $row) {
    if (isset($totals[$row['Date']]) ) {

        $totals[$row['Date']]['TotalCount1']
            = $totals[$row['Date']]['TotalCount1'] + $row['Count1'];

        $totals[$row['Date']]['TotalCount2']
            = $totals[$row['Date']]['TotalCount2'] + $row['Count2'];

    } else {

        $totals[$row['Date']] = array(
             'Date' => $row['Date'],
             'TotalCount1' => $row['Count1'],
             'TotalCount2' => $row['Count2'],
        );

    }
}