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POFormatting problem with PHP DateTime Difference when used as part of an equation
 

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  1. POFormatting problem with PHP DateTime Difference when used as part of an equation
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    <p>I'm trying to write a simple invoicing system. I wanted to use DateTime Diff to calculate the cost of each invoice.</p> <p>So far I have:</p> <pre><code>/* In this example $dayLength and $ratePerSec don't really matter but we will use the hypotethical values of 8.0 and 0.0054 for now */ $date1 = new DateTime( "Time1FromDatabase", [DateTimeZoneOfChoice] ); $date2 = new DateTime( "Time2FromDatabase", [DateTimeZoneOfChoice] ); $diff = $date2-&gt;diff( $date1 ); $lenInSec = $diff-&gt;format("%y")*365*$dayLength*3600 + $diff-&gt;format("%d")*$dayLength*3600 + $diff-&gt;format("%h")*3600 + $diff-&gt;format("%i")*60 + $diff-&gt;format("%s"); $cost = $lenInSec * $ratePerSecond; </code></pre> <p>When I try to output cost using the $lenInSec generated from DateTime Diff I get really odd results. Sometimes, anywhere from 1 in 3 and 1 in 50 times, I get the correct value of say 460.25. A lot of the time I just get a random string of letters, numbers or symbols, such as: þ50.</p> <p>I've found that if I echo out the result 2+ times then on the final output I get the expected result perfectly.</p> <p>My temporary fix at the moment is, in the getCost() function, to run:</p> <pre><code>ob_start(); echo $cost; echo $cost; ob_clean(); return $cost; </code></pre> <p>And so far this seems to fix the problem and I seem to get the expected result every time but it's a bit weird.</p> <p>I know it's the DateTime Diff in the equation because if I replace it with the old-style:</p> <pre><code>strtotime( "Time2FromDatabase") - strtotime( "Time1FromDatabase") </code></pre> <p>it works perfectly every time.</p> <p>I also have a running total cost:</p> <pre><code>$totalCost += $cost; </code></pre> <p>Outputting $totalCost always outputs the correct value regardless of whether I use the DateTime Diff method or the strtotime method.</p> <p>I've also tried using intval. (int) and (string) casts on the $lenInSec variable before using it in the equation and it has no effect.</p> <p>Can anyone give any clues as to why this is happening? Is it a(n) (un)known bug in PHP's DateTime/Diff classes?</p> <p>EDIT:</p> <pre><code>$date1 = new DateTime( "2011-09-04 09:00:00", new DateTimeZone("UTC") ); $date2 = new DateTime( "2011-09-04 18:00:00", new DateTimeZone("UTC") ); //Essentially 1 day of work $rate = 200.00; //Per Day $ratePerSec = 0.00617283950617283950617283950617; // $rate / (9 hours * 3600 seconds ) $lenInSec = 32400; // From the diff calculation $cost = $lenInSec * $ratePerSec; // Cost should now equal 200. echo $cost; // Sometimes outputs 8, other times 200, other times þ50. //I think the þ50 is when you have a number like 425.50 where þ is the 425. $totalCost += $cost; echo number_format($totalCost,2); /* Will return the correct value of all the $cost variables added no matter what the individual $cost variables are output as, in this case 200.00 */ </code></pre>
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    1. COAre you sure that the used datetime formats are the same? Try using the `DateTime::createFromFormat()` method. Other than that ... except you can replace the `%y` and `%d` with `%a`(for total days) I don't think that there's anything wrong on your part. There are a number of warnings for inacurracies in the user comments for `DateTime::diff()`, and since this is a relatively new extension for PHP - I guess it could be a bug.
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    2. COOK thanks. I'll give your suggestions a try and report back. Although I'm pretty sure they DateTime formats are the same. They both come from a datetime field in a Mysql database.
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    3. COCreateFromFormat() didn't change anything unfortunately.
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