Push rows with default values into an array containing dates so there are no gaps between dates

Question

I have an array of rows with date values, but not all dates are guaranteed between the first and last row. I need to add rows so that every date has a row (a default value should be applied for the secondary column value).

Sample input:

$array = [
    ['date' => '2017-09-01', 'total' => 4],
    ['date' => '2017-09-03', 'total' => 6],
    ['date' => '2017-09-04', 'total' => 1],
    ['date' => '2017-09-05', 'total' => 3],
    ['date' => '2017-09-09', 'total' => 5]
];

I want to fill the date even if my query has no records on that date! How can I add the missing date index to the array. The dates are to be sequential/contiguous.

Desired output:

[
    ['date' => '2017-09-01', 'total' => 4],
    ['date' => '2017-09-02', 'total' => 0],
    ['date' => '2017-09-03', 'total' => 6],
    ['date' => '2017-09-04', 'total' => 1],
    ['date' => '2017-09-05', 'total' => 3],
    ['date' => '2017-09-06', 'total' => 0],
    ['date' => '2017-09-07', 'total' => 0],
    ['date' => '2017-09-08', 'total' => 0],
    ['date' => '2017-09-09', 'total' => 5]
]

Answer 1

Extended solution with DateTime object, array_map and range functions:

$arr = [
        ['date' => '2017-09-01', 'total' => 4],
        ['date' => '2017-09-07', 'total' => 6],
        ['date' => '2017-09-09', 'total' => 7]
];

$result = [];
foreach ($arr as $k => $item) {
    $d = new DateTime($item['date']);
    $result[] = $item;
    if (isset($arr[$k+1])) {
        $diff = (new DateTime($arr[$k+1]['date']))->diff($d)->days;
        if ($diff > 1) {
            $result = array_merge($result , array_map(function($v) use($d){
                $d_copy = clone $d;
                return [
                    'date' => $d_copy->add(new DateInterval('P' . $v. 'D'))->format('Y-m-d'),
                    'total' => 0
                ];
            }, range(1, $diff-1)));
        }
    }
}

print_r($result);

The output:

Array
(
    [0] => Array
        (
            [date] => 2017-09-01
            [total] => 4
        )

    [1] => Array
        (
            [date] => 2017-09-02
            [total] => 0
        )

    [2] => Array
        (
            [date] => 2017-09-03
            [total] => 0
        )

    [3] => Array
        (
            [date] => 2017-09-04
            [total] => 0
        )

    [4] => Array
        (
            [date] => 2017-09-05
            [total] => 0
        )

    [5] => Array
        (
            [date] => 2017-09-06
            [total] => 0
        )

    [6] => Array
        (
            [date] => 2017-09-07
            [total] => 6
        )

    [7] => Array
        (
            [date] => 2017-09-08
            [total] => 0
        )

    [8] => Array
        (
            [date] => 2017-09-09
            [total] => 7
        )
)