PHP calculating number of days between 2 dates

Question

I am developing a web application which revolves around dates.

I need to calculate numbers based around days elasped, for example - pseudo code

$coun         


        

Answer 1

You could create a loop which goes to the next day in the $count_only array, from the $start_date and stopping (returning from the function) upon reaching the $end_date.

function number_of_days_between($start_date, $finish_date, $count_only) {
    $count  = 0;
    $start  = new DateTime("@$start_date");
    $end    = new DateTime("@$finish_date");
    $days   = new InfiniteIterator(new ArrayIterator($count_only));
    foreach ($days as $day) {
        $count++;
        $start->modify("next $day");
        if ($start > $end) {
            return $count;
        }
    }
}

Answer 2

Just a bit faster approach than "iterating through all days":

$count_only = array(1, 3, 5); // days numbers from getdate() function
$start_date = 1298572294;
$finish_date = 1314210695;

function days($start_date, $finish_date, $count_only)
{
    $cnt = 0;

    // iterate over 7 days
    for ($deltaDays = 0; $deltaDays < 7; $deltaDays++)
    {
        $rangeStart = $start_date + $deltaDays * 86400;

        // check the weekday of rangeStart
        $d = getDate($rangeStart);
        if (in_array($d['wday'], $count_only))
        {
            $cnt += ceil(($finish_date - $rangeStart) / 604800);
        }
    }

    return $cnt;
}

The idea is to count number of weeks using some additional offsets for mondays, tuesdays, wednesdays etc.

Answer 3

Of course there is a way :-)

The days that have been elapsed is simply

$elapsed_days = floor(($finish_date-$start_date) / 86400);

This will not get the result you need. What you could do is the following (pesudo)code:

$elapsed_days = floor(($finish_date-$start_date) / 86400);
for(int $i=0;$i<$elapsed_days;$i++){
  $act_day_name = strtolower(date('l',$start_date+$i*86400));
  if(in_array($act_day_name,$count_only){
    // found matching day
  }
}

What I do: I iterate over every day which is between the both dates, get the day-name with date('l'); and check if it's within the array. There may be some fine tuning need to be done, but this should get you going.

Answer 4

You can simplify this considerably by calculating how many complete weeks fall between the two specified dates, then do some math for the beginning/end partial weeks to account for dangling dates.

e.g.

$start_date = 1298572294;  // Tuesday
$finish_date = 1314210695; // Wednesday

$diff = 1314210695-1298572294 = 15638401 -> ~181 days -> 25.8 weeks -> 25 full weeks.

Then it's just a simple matter of checking for the dangling dates:

Tuesday -> add 2 days for Wednesday+Friday to get to the end of the week
Wednesday -> add 1 day for Monday to get to the beginning on the week

Total countable days = (25 * 3) + 2 + 1 = 75 + 3 = 78 countable days