问题
Why the leading zero in the month parameter making wrong output?
echo date("Y-m-d", mktime(0, 0, 0, 09, 23, 2013));//output 2012-12-23
echo date("Y-m-d", mktime(0, 0, 0, 9, 23, 2013));//output 2013-09-23
回答1:
From https://bugs.php.net/bug.php?id=55327:
Numbers with leading 0's are octal. 08 is an invalid value. See http://php.net/integer
If you prefix a number with a leading 0, it marks the number as Octal. The octal numeral system uses the digits 0 to 7. So, 08 and 09 doesn't exist and are invalid.
The second statement is correct, and that's the correct method:
echo date("Y-m-d", mktime(0, 0, 0, 9, 23, 2013));
回答2:
We can make this parameter as a string and it will work.
Try this:
echo date("Y-m-d", mktime(0, 0, 0, '09', 23, 2013));//output 2012-12-23
来源：https://stackoverflow.com/questions/19160334/leading-0-in-month-parameter-making-wrong-output