Bug #76731 [Com]: Date time format parsing is wrong for format Ynd

Edit report at https://bugs.php.net/bug.php?id=76731&edit=1 ID: 76731 Comment by: a at b dot c dot de Reported by: remy dot fox at simbuka dot com Summary: Date time format parsing is wrong for format Ynd Status: Open Type: Bug Package: Date/time related PHP Version: 7.2.8 Block user comment: N Private report: N New Comment: In short: createFromFormat("Ymd", "2000101") should be rejected because it doesn't have enough digits, right? There should be four for the year, two for the month, and two for the day. The test case can be simplified: $date = DateTime::createFromFormat("d", "1"); var_dump($date); Of the other "leading zero" format specifiers, "m", "h" and "H" also parse, but "i" and "s" both fail. Previous Comments: ------------------------------------------------------------------------ [2018-08-12 18:06:44] remy dot fox at simbuka dot com You are right that sometimes there is ambiguity. For example, if we take the string '2000111' then for the format 'Ynj' it could mean either 11 january or 1 november. This is because both the month and day specifiers are unpadded. In my example there is no ambiguity though. Both the month and day specifier are padded in 'Ymd' and so the parsing should fail (i.e. return false), because the zero in position 6 is used twice now. ------------------------------------------------------------------------ [2018-08-12 12:49:59] requinix@php.net I don't think it's reasonable to require PHP to check for ambiguity. It's extra processing cycles for inputs when in nearly all cases, and I would even say all cases that aren't due to bad decisions, the input is not ambiguous. Really, strings like "2000101" are weird - surely anyone serializing a date will use 8 digits, right? I mean, what date is it supposed to represent anyways? You say Oct 1 but it could be Jan 01 too. As a human, how would you decide? I'd add a warning to the docs that m/n and d/j (and others) work best when (a) the date parts are always the full length with zero padding if needed, or (b) there is a clear separation between the parts. And that otherwise the result is undefined. ------------------------------------------------------------------------ [2018-08-12 12:21:27] remy dot fox at simbuka dot com Description: ------------ The parsing of the date formats 'Ynd' and 'Ymd' gives a wrong result when segment in the date are not separated by any characters. There may be similar issues with other date time format specifier combinations too, but I haven't tested them. Test script: --------------- $date = DateTime::createFromFormat("Ymd", "2000-10-1"); var_dump($date); $date = DateTime::createFromFormat("Ymd", "2000101"); var_dump($date); Expected result: ---------------- As we can see, the first $date returns false, which is correct. After all the day value was not padded with a zero. In the second example, the zero could be interpreted as either part of the month (i.e. october) or as padding for the day value. The result does not return false but it should. object(DateTime)#2 (3) { ["date"]=> string(26) "2000-10-01 05:18:02.000000" ["timezone_type"]=> int(3) ["timezone"]=> string(10) "US/Pacific" } ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=76731&edit=1