Php减去两个日期，不同的日期返回错误的结果

Question

I am trying to subtract two dates using php. Dateone is stored in the database while datetwo is the current date. Now, i have this strange scenario: Dateone is 23-03-13 Date two is 02-04-13

Using different subtraction methods, give different results.

Method One - Returns -21

$sqldate ="SELECT exam_date FROM exam_table";
$fetchdate = mysql_query($sqldate);
$rowdate = mysql_fetch_array($fetchdate);
//Fetch the date stored in the database
$dateone = $rowdate['exam_date'];
//Calculate the current date today
$datetwo =date('d-m-y');
//Calculate the diff between the two dates
$datediff = $datetwo-$dateone;

In this case, $datediff returns -21

Method Two - Returns -7639

$sqldate ="SELECT exam_date FROM exam_table";
$fetchdate = mysql_query($sqldate);
$rowdate = mysql_fetch_array($fetchdate);
//Fetch the date stored in the database
$dateone = $rowdate['exam_date'];
//Calculate the current date
$datetwo =date('d-m-y');
//Calculate the diff between the two dates
$datetime1 = strtotime("$dateone");
$datetime2 = strtotime("$datetwo");
//seconds between the two times
$secs = $datetime2 - $datetime1;
$days = $secs / 86400;

In this scenario, $days returns -7639

Answer 1

Yeah issue is because your date format is not standard to get difference. You need to inform your current format to date & convert it to standard one to get correct difference.

$datetime1 = DateTime::createFromFormat('d-m-Y', '23-03-13'); #In you case it is considering 13-03-2023
$datetime1->format('d-m-YY');
$datetime2 = DateTime::createFromFormat('d-m-Y', '02-04-13'); #In you case it is considering 13-04-2002
$datetime2->format('d-m-YY');
$interval = $datetime1->diff($datetime2);
echo $interval->format('%R%a days'); #output +10 days

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Note: PHP version should be >= 5.3.0.