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(Looks like something's wrong with my environment / system. Am analyzing it currently. Every logical answer was tried and it failed. So, will report back once I have more to share. Thanks for the answers!)

I have written some simple PHP code to calculate the duration between two dates, and do some basic arithmetic, to calculate some percentage value.

I am at a loss of clues on why this is not working! Seems to me that a variable is treated as an integer on one line and a string on another. 

$start_DT = new DateTime($startdate); // e.g. 2011-06-07 $end_DT = new DateTime($enddate); // e.g. 2011-06-14 $today_DT = new DateTime("now"); // 2011-06-09 $duration = date_diff($end_DT, $start_DT)->d; $days_remaining = date_diff($end_DT, $today_DT)->d; echo $days_remaining; // This outputs a value of "4" in my specific case echo $duration; // This outputs a value of "7" for my specific case. $percentage_dur_complete = $days_remaining / $duration; echo $percentage_dur_complete; // This gives a value of NAN // This line says that I am dividing my zero, to imply that // $duration might be a string. $percentage_dur_complete = $days_remaining / (float) $duration;

Am I missing something basic? I am a relative newbie (2 months) to PHP. I really hope (with the risk of appearing stupid) that there's something I've missed out.

Thanks!

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  • date_diff returns a DateInterval, not an integer. Commented Jun 9, 2011 at 21:57
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    One way to check what type each variable is before the division is to use var_dump( $myvar ), which will tell you the type and value of $myvar. More info here: php.net/manual/en/function.var-dump.php Commented Jun 9, 2011 at 21:59
  • Yes, I figured that out. I am accessing its member variable for days (->d) to get the actual integer within it. Commented Jun 9, 2011 at 22:01
  • If I do var_dump, then both numbers are integers and $percentage_dur_complete contains a proper number. There must be something else wrong. Are you sure $startdate and $enddate are correctly set? Commented Jun 9, 2011 at 22:02
  • @Paul Sonier - Maybe the OP knows that? Maybe that's why the OP selects the $d member of the object? Maybe you should look at all of the little squigglies before putting people down? And maybe everybody else should too before upvoting a snide and wrong remark? Commented Jun 9, 2011 at 22:04

4 Answers 4

Reset to default
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try 

$percentage_dur_complete = (int)$days_remaining / (int)$duration;

EDIT: This works for me... 

<?php $startdate = '2011-06-05'; $enddate = '2011-06-12'; $today_DT = new DateTime("now"); $start_DT = new DateTime($startdate); // e.g. 2011-06-07 $end_DT = new DateTime($enddate); $duration = date_diff($end_DT, $start_DT)->d; $days_remaining = date_diff($end_DT, $today_DT)->d; var_dump ($duration); var_dump ($days_remaining); $percentage_dur_complete = $days_remaining / $duration *100; echo ($percentage_dur_complete); ?>

If it doesnt for you, it is most definitely an issue with your PHP installation/version!

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2 Comments

Sleep doesn't work, although I wonder why it makes sense to add? Seems a bit unrelated?
Yes, its likely something with my system that's wonky. Thanks for the response. Will have to figure out what's going on at my end
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I took your code and modified it a bit (formatted output, but more importantly passed direct strings into the DateTime functions):

$start_DT = new DateTime('2011-06-07'); $end_DT = new DateTime('2011-06-14'); $today_DT = new DateTime("now"); $duration = date_diff($end_DT, $start_DT)->d; $days_remaining = date_diff($end_DT, $today_DT)->d; echo $days_remaining . "<br>"; echo $duration . "<br>"; $percentage_dur_complete = $days_remaining / $duration; echo $percentage_dur_complete . "<br>"; $percentage_dur_complete = $days_remaining / (float) $duration; echo $percentage_dur_complete . "<br>";

And I'm getting output that looks like this:

5 7 0.71428571428571 0.71428571428571

My hunch is that you're not passing what you think you're passing to generate $start_DT and $end_DT.

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13 Comments

I tried this out. What's wierd(er) is that every OTHER operation with $duration fails, and every OTHER works. So, if I add an extra echo for $duration, my own code works OK. Can't figure out why
I'm not sure what you mean? You mean that it alternates between working and not working?
So, if I copy paste your code as-is, this is what I get: 3 7 NAN 0.42857142857143
Yes, every alternate operation with $duration works. I know it sounds silly. :(
What locale are you in? Maybe the DateTime constructor is not parsing the date correctly because it's looking for another format.
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I'll bet that DateTime's constructor is having trouble with your incoming dates. Try this:

$startdate = "2011-06-07"; $enddate = "2011-06-14"; $start_DT = DateTime::createFromFormat('Y-m-j',$startdate); $end_DT = DateTime::createFromFormat('Y-m-j',$enddate); $today_DT = new DateTime("now"); $duration = date_diff($end_DT, $start_DT)->d; $days_remaining = date_diff($end_DT, $today_DT)->d; echo $days_remaining . "<br>\n"; echo $duration . "<br>\n"; $percentage_dur_complete = $days_remaining / $duration; echo $percentage_dur_complete . "<br>\n"; $percentage_dur_complete = $days_remaining / (float) $duration; echo $percentage_dur_complete . "<br>\n";

Make sure the format string matches how you're passing in your date strings (i.e. 'j' for days with leading zero, 'd' for days without).

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1 Comment

Thanks. This worked for a bit, and then stopped working. I think something is wrong in my install. Will reinstall everything / try it on a different system. Even if I take your code as is, it works intermittently. Makes me believe that its my system
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I had the same problem. I was using PHP 5.3.1 and I upgraded to 5.4.17 to solve the issue. Don't waste time trying to find a workaround like I did initially.

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1 Comment

is your answer really related to date_diff issue that is exposed in the question?

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