I am developing a web application which revolves around dates.
I need to calculate numbers based around days elasped, for example - pseudo code
$count_only = array('monday', 'wednesday', 'friday'); //count only these days
$start_date = 1298572294; // a day in the past
$finish_date = 1314210695; //another day
$var = number_of_days_between($start_date, $finish_date, $count_only);
Is there a way determine how many full days have elapsed, while only counting certain days?
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
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;
}
}
}
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.
$act_day_name to lowercase and switch the incorrect order of in_array arguments, and I will upvote this
date('l') returns first letter uppercase strings "Sunday through Saturday"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.
