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regex function to match a date in yyyy-mm-dd format accounting for length of month


terungwa

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I have set up a function to validate user input date in yyyy-mm-dd format taking into account the following possibilities:

  1. the length of the month
  2. February 29th when the year is not a leap year

When I run the code, I do not get any feedback whatsoever, when it should.

This is the code below and I would appreciate your thoughts:

if(!function_exists('checkdate'))
{
	function checkdate($date, $checkyear, $currentmonth)
	{
		if($checkyear == 0)//if it is not a leap year
		{
			// if current month is february
			if($currentmonth == 2)
			{
				if(!preg_match("/^(20)\d\d[-](0[1-9]|1[012])[-](0[1-9]|1[0-9]|2[0-8])$/", $date))
				{
					// set error for date field
					return ($error = 'Invalid Date!');
				}
				return ($error = 'valid Date!');
			}
			// if current months are april, june, september or november
			elseif($currentmonth == 4 || $currentmonth == 6 || $currentmonth == 9 || $currentmonth ==11)
			{
				if(!preg_match("/^(20)\d\d[-](0[1-9]|1[012])[-](0[1-9]|1[0-9]|2[0-8]|3[0])$/", $date))
				{
					// set error for date field
					return ($error = 'Invalid Date!');
				}
				return ($error = 'valid Date!');
			}
			else
			{	
				if(!preg_match("/^(20)\d\d[-](0[1-9]|1[012])[-](0[1-9]|[12][0-8]|3[01])$/", $date))
				{
					// set error for date field
					return ($error = 'Invalid Date!');
				}
				return ($error = 'valid Date!');
			}
		}
		elseif($checkyear == 1)//if it is a leap year
		{
			// if current month is february
			if($currentmonth == 2)
			{
				if(!preg_match("/^(20)\d\d[-](0[1-9]|1[012])[-](0[1-9]|1[0-9]|2[0-9])$/", $date))
				{
					// set error for date field
					return ($error = 'Invalid Date!');
				}
				return ($error = 'valid Date!');
			}
			// if current months are april, june, september or november
			elseif($currentmonth == 4 || $currentmonth == 6 || $currentmonth == 9 || $currentmonth ==11)
			{
				if(!preg_match("/^(20)\d\d[-](0[1-9]|1[012])[-](0[1-9]|1[0-9]|2[0-9]|3[0])$/", $date))
				{
					// set error for date field
					return ($error = 'Invalid Date!');
				}
				return ($error = 'valid Date!');
			}
			else
			{	
				if(!preg_match("/^(20)\d\d[-](0[1-9]|1[012])[-](0[1-9]|[12][0-9]|3[01])$/", $date))
				{
					// set error for date field
					return ($error = 'Invalid Date!');
				}
				return ($error = 'valid Date!');
			}
		
		}
	}
$todate = getdate();
$currentmonth = $todate['mon'];
$checkyear = date('L');
$date = 2014-02-31;
echo checkdate($date, $checkyear, $currentmonth);
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php has a function called checkdate(), which means your function definition isn't being made and your code is likely throwing php errors when you call php's built-in checkdate() function with those parameters.

 

you need to ALWAYS have php's error_reporting set to E_ALL and have display_errors set to ON, when developing code, to get php to help you.

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Besides that, the implementation is horrible. Sorry.

 

Regexes are for patterns. They're not suitable for range checks. That's what we have the mathematical operators “<”, “<=”, “>” and “>=” for.

 

It's also insane to do date calculations by hand. Even if you actually manage to find a PHP version which doesn't have checkdate(), the basic date functions are always available. I mean, handling dates is one of the core features of every language. And, yes, PHP can do it as well.

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