isValidDate

isValidDate.php

/**
 * 
 * Check if the given date is valid 
 * @param string $date
 *
 * @param string $separator
 *
 * @param string $format defines the order which year month and day are in the $date string
 *                       this string supports "d" for days "m" for month and "y" for year
 *
 * @param int|bool $lower2DigitsDate (optional default 1950) if the given date is 
 *                                   defined as 2 digits value it will be adjusted
 *                                   according to this value if the parameter is false 
 *                                   the correction will not be performed
 * 
 * @example $date = '2012-08-30'; $validDate = isValidDate($date, '-', 'ymd');
 * @example $date = '30/08/2012'; $validDate = isValidDate($date, '/', 'dmy');
 * @example $date = '08/30/2012'; $validDate = isValidDate($date, '/', 'mdy');
 * @example $date = '08/30/12';   $validDate = isValidDate($date, '/', 'mdy');
 * 
 * @return boolean
 */
function isValidDate($date, $separator = '/', $format = 'dmy', $lower2DigitsDate = 1950){
	/*
	 * Detect the Datetime structure
	 */
	$yearIndex 	= strpos($format, 'y');
	$monthIndex 	= strpos($format, 'm');
	$dayIndex 	= strpos($format, 'd');
	
	/*
	 * split the string date into an array of three elements according to given separator
	 */
	$dateElements = preg_split('#'. preg_quote($separator, '#') . '#', $date);
	/*
	 * Check for EXACT 3 parts in the date 
	 */
	if(count($dateElements)!=3) return false;
	
	$day 	= intval($dateElements[$dayIndex]);
	$month 	= intval($dateElements[$monthIndex]);  
	$year 	= intval($dateElements[$yearIndex]);
	
	/*
	 * Convert 2 digits year in 4 digits year
	 */
	if($year<100 && $lower2DigitsDate !==false){
		$marker = ($lower2DigitsDate%100);
		if($year<$marker) $year += 100;
		$year = $lower2DigitsDate-$marker + $year;

		$dateElements[$yearIndex] = $year;
	}
	
	
	$monthDays 		= array( 0, 31,	28, 31, 30, 31, 30, 31, 31, 30, 31, 30,31);

	/**
	 * Exception on introduction of Gregorian Calendar
	 * @see http://diegolamonica.info/howto-detect-if-typed-date-is-valid/#comment-5426
	 */
	if($year==1582 && $month==10 && $day>4 && $day<15) return false;
	
	/**
	 * Feb has 29 days in the leap years
	 * @see http://en.wikipedia.org/wiki/Leap_year#Algorithm
	 */
	$leapYear 		= ($year % 4 == 0 && ($year % 100 != 0 || $year % 400 == 0) ); 
	
	if($leapYear) $monthDays[2] = 29;
	
	// Output the adjusted date (with 4 digits year)
	$date = implode($separator, $dateElements);
	
	/*
	 * Check if the day of the month is into the range
	 */ 
	return ($monthDays[$month] >= $day &&  $day>0);	
		
}