PHP OOP DateTime ModifyDate小数位错误

Question

If I use the following code

$averageWeeks = 2.7;
$laidDate->modify('+'.$averageWeeks.' week');

I get the date 31st May 2014 returned, whereas if i use the following code

$averageWeeks = 3;
$laidDate->modify('+'.$averageWeeks.' week');

I get the date 3rd May 2014 which is right. Is there any way I can use decimal places in the date modify method?

Answer 1

Assuming you're starting at April 12th, then May 3rd would be 3 weeks and May 31st would be 7 weeks. So my guess is that when you pass "2.7", it is ignoring the "2." portion of that string.

You could consider calculating the number of days to add separately, such as:

$averageWeeks = 2.7;
$averageDays = floor($averageWeeks * 7);
$laidDate->modify('+'.$averageDays.' days');

Consider also that 2.7 weeks is 18.9 days. By taking the floor, We are adding 18 days. It doesn't make since to add fractional days here, unless you intend to change the time of day as well. If you did, you'd have to do some additional math, as it doesn't appear that either modify or add will support fractional values. You could do something like this:

$averageWeeks = 2.7;
$averageSeconds = floor($averageWeeks * 7 * 24 * 60 * 60);
$laidDate->modify('+'.$averageSeconds.' seconds');

But you might be fooling yourself if you think this time is accurate, since not every local day has exactly 24 hours in it, due to daylight saving time transitions.