Checking For Leap Year Using PHP

By  on  

One part of programming that seems pretty static is dealing with dates. The calendar is a set system of rules that doesn't look to change. The only part of the calendar that can be variable is a leap year, which changes every four years (obviously).

Using pure PHP ternary logic, much like the PHP Function - Calculating Days In A Month, I posted a few weeks back, you can check to see if a year is a leap year.

The Code

function is_leap_year($year) {
	return ((($year % 4) == 0) && ((($year % 100) != 0) || (($year % 400) == 0)));
}

Recent Features

  • By
    CSS vs. JS Animation: Which is Faster?

    How is it possible that JavaScript-based animation has secretly always been as fast — or faster — than CSS transitions? And, how is it possible that Adobe and Google consistently release media-rich mobile sites that rival the performance of native apps? This article serves as a point-by-point...

  • By
    Page Visibility API

    One event that's always been lacking within the document is a signal for when the user is looking at a given tab, or another tab. When does the user switch off our site to look at something else? When do they come back?

Incredible Demos

  • By
    jQuery Chosen Plugin

    Without a doubt, my least favorite form element is the SELECT element.  The element is almost unstylable, looks different across platforms, has had inconsistent value access, and disaster that is the result of multiple=true is, well, a disaster.  Needless to say, whenever a developer goes...

  • By
    Geolocation API

    One interesting aspect of web development is geolocation; where is your user viewing your website from? You can base your language locale on that data or show certain products in your store based on the user's location. Let's examine how you can...

Discussion

  1. Placing a function call as an argument default will result in a fatal error. Also, give this version a shot:

    function is_leap_year( $year = NULL )
    {
        if_numeric( $year ) || $year = date( 'Y' );
        return checkdate( 2, 29, ( int ) $year );
    }
  2. Whoops, small typo… if_numeric( $year ) should be is_numeric( $year )… :x

  3. Tamlyn

    Better yet, use date('L') which returns 1 if it’s a leap year, 0 if it isn’t.

  4. I do agree with tamlyn, why you dont use date function??
    It can makes a load fasting right?

  5. Travis

    date(‘L’) is way better because leap year is not every 4 years.

  6. Date("L") only tell you in a given year, default is the year today.
    If you need to know whether previous or next year is a leap, you must reset the date.
    It could affect the system.

    • Indra, you can always pass the timestamp as second parameter to date function:

      echo date('L', mktime(1, 1, 1, 1, 1, 2005));
      
  7. I think this is a better example relating to the function. Also provided example for anyone looking for true/false as I was in this instance.

    /* for true or false */
    function is_leap_year($year)
    {
    	return ( date ('L', mktime(1,1,1,1,1, $year) ) === 1 ) ? true : false;
    }
    /*for 0 or 1 Whether it's a leap year: 1 if it is a leap year, 0 otherwise. */
    function is_leap_year($year)
    {
    	return date ('L', mktime(1,1,1,1,1, $year) );		
    }
    
  8. Habibur Rahaman
    <?php
    $day = "";
    for($i=0; $i<4; $i++)
    {
        $day =  date("d", mktime(0, 0, 0, 2, 29, date("Y")+$i));
        if($day == 29)
        {
            $year = date("Y")+$i;
            break;
        }
    }
    echo "The next leap year is 29th February $year";    
    ?>
    
    
  9. Milan Dvořák

    code of Habibur Rahaman will not work for example for the year 1897, because 1900 is not leap year.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!