[RESOLVED] User Input - Dates

[WDPEjoe]

Outline:
(1) Internationalization (ie date formats used by countries other than the US) is not a concern right now
(2) Users should be able to input anything reasonable and the parsing mechanism glean the user's intent
(3) The parsing mechanism needs to reliably fail when there is ambiguity (the only thing worse than annoying users ["please input dates as mm/dd/yyyy"] is to "validate" & process the wrong date)

The function I use now (home-brewed) is hacked together and I have grown to like it less and less. Everyone who's written an application has dealt with this problem -- how do you handle it?

[burfo]

Normally I prefer to do date validation client-side with javascript, at least initially. But this is what I use in PHP:

function isValidDate($sDate) {
	if (ereg('^([0-9]{1,2})[-/]([0-9]{1,2})[-/]([0-9]{2,4})$', $sDate, $regs)) {
		return checkdate($regs[1], $regs[2], $regs[3]);
	}
	return false;
}

[NogDog]

I prefer to provide 3 separate select elements for year, month, and day with each returning an integer value, then validating them via [man]check_date/man and converting them into a single "UNIX time" value via [man]mktime/man, thereby removing all ambiguity. But if you really need to allow them to type in a date, [man]strtotime/man can convert most standard formats into a UNIX time value. You can check to see if it fails as a method of error checking.

$date = strtotime($_POST['date']);
if((phpversion() < 5.1 and $date == -1) or  $date === false)
{
   // input error
}

[burfo]

Just using strtotime() without any other validation won't always yield what you expect, though. For example:

$ts = strtotime("2000");
echo "timestamp: ".$ts."<br>";
echo date("r", $ts);

Output:

timestamp: 1198378800
Sat, 22 Dec 2007 20:00:00 -0700

[NogDog]

Which is yet another reason that I prefer an input mechanism which does not allow any ambiguity, either separate <select> elements or some kind of calendar interface (whether JavaScript, PHP, or AJAX). 🙂

[WDPEjoe]

I agree on the front-end issue. Any time it works into the flow of the UI, I use a datepicker. However, there are some instances (in a long form where you're using tab a lot, for example) that it just makes more sense to let the user type the date into a text field.

I am aware of the strtotime function and will probably simply use that. I'm really not into re-inventing the wheel, but I wanted to check with you guys to see if there was anything better/more insightful that I missed.

Thank you for the discussion.