显示具有先前值的运行总计

Question

I have an array like this

Array
    (
    [2013-03-12] => Array
        (
            [total_clicks] => 2266
            [total_unique_clicks] => 177
        )

    [2013-03-19] => Array
        (
            [total_clicks] => 2647
            [total_unique_clicks] => 241
        )

    [2013-03-20] => Array
        (
            [total_clicks] => 2656
            [total_unique_clicks] => 245
        )
     )

Now I am using the following code for displaying the values

$current=strtotime($from);
$last=strtotime($to);
while($last >= $current){
    $current_date=date("Y-m-d",$last);
    echo $daily_click[$current_date]['total_unique_clicks'];
    $last=strtotime("-1 day",$last);
}

This is displaying the values but if there is no value for a date say '2013-03-18' I need to display the previous value from the array that is with the index 2013-03-12 and the value is 177. It is actually a running total and so i need to display this for other dates with out values. That is it should display the previous count until it is changed. how can I do this ?

I need this order for the dates as I need to show from the latest date first and decreasing

Answer 1

// get an array of the recorded dates in descending order
$descDateOrder = $daily_click;
ksort($descDateOrder);
$descDateOrder = array_keys(array_reverse($descDateOrder));

$current=strtotime($from);
$last=strtotime($to);

// initialize to the most recent date <= $last
$prev_key = 0;
for($i = 0; $i < count($descDateOrder); $i++) {
    if (strtotime($descDateOrder[$i]) <= $last) {
        $prev_key = $i;
        break;
    }
}

while($last >= $current) {
    $current_date=date("Y-m-d",$last);

    if ($descDateOrder[$prev_key] == $current_date) {
        // use oldest date if we go past it (could break instead, to stop)
        $prev_key = min(count($descDateOrder) - 1, $prev_key + 1);
    } else {
        $current_date = $descDateOrder[$prev_key];
    }

    echo $daily_click[$current_date]['total_unique_clicks'];

    $last=strtotime("-1 day",$last);
}