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
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

  • By
    5 More HTML5 APIs You Didn’t Know Existed

    The HTML5 revolution has provided us some awesome JavaScript and HTML APIs.  Some are APIs we knew we've needed for years, others are cutting edge mobile and desktop helpers.  Regardless of API strength or purpose, anything to help us better do our job is a...

Incredible Demos

  • By
    iPad Detection Using JavaScript or PHP

    The hottest device out there right now seems to be the iPad. iPad this, iPad that, iPod your mom. I'm underwhelmed with the device but that doesn't mean I shouldn't try to account for such devices on the websites I create. In Apple's...

  • By
    Facebook Open Graph META Tags

    It's no secret that Facebook has become a major traffic driver for all types of websites.  Nowadays even large corporations steer consumers toward their Facebook pages instead of the corporate websites directly.  And of course there are Facebook "Like" and "Recommend" widgets on every website.  One...

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!