PHP has a number of "hidden" abilities contained within its functions. One of those is the ability to detect if its a leap year using the date() function.

Lets look at the code required to accomplish this.

print date('L');

As you can see, the code is minimal and straightforward. In the above example you are basically asking if the current year is in fact a leap year. Lets expand on that example and wrap it in a function to quickly validate any date.

function isLeapYear($year=null)
{
	if(is_null($year))
	{
		return date('L');
	}
	else
	{
		return date('L', strtotime($year . "-01-01"));
	}
}

Now that the function is complete, lets look at an example usage.

if(isLeapYear(2008))
{
	print "2008 is a leap year";
}
if(isLeapYear(2009))
{
	print "2009 is NOT a leap year";
}

I hope you found this little tutorial useful for the next time you need validate if a date is a leap year.