How to check whether a year is a leap year or not in PHP

These are different ways to find out whether a year is a leap year or not.

Leap Year Program using checkdate() function

The checkdate() function is used to check a valid date in a month and year. It always returns a Boolean value.

Syntax of checkdate() function

bool checkdate(int $month, int $day, int $year);

In the checkdate() function, we have passed '2' in the first parameter, i.e. February month, '29' in the second parameter, i.e. 29 days, and the third parameter, $year is a variable that accepts year.

<?php
function checkLeapYear($year) {
    return checkdate(2, 29, $year);
}
echo checkLeapYear(2016) ? "2016 is a leap year." : "2016 is not a leap year. ";
echo '<br/>';
echo checkLeapYear(2017) ? "2017 is a leap year." : "2017 is not a leap year. ";
?>

Output of the above code

2016 is a leap year.
2017 is not a leap year.

Using Leap Year Logic

Most of us already know the logic to check for a leap year in the Gregorian calendar. These are the three criteria that must be met to identify leap years-

• The year can be evenly divided by 4,
• If the year can be evenly divided by 100, it is NOT a leap year, unless;
• The year is also evenly divisible by 400. Then it is a leap year.

The following code implements this logic -

<?php

// function to test if leap year
function checkLeapYr($year) {
 $ret = (($year%400 == 0) || ($year%4 == 0 && $year%100 != 0)) ? true : false;
 return $ret;
}

echo checkLeapYr(2016) ? "2016 is a leap year." : "2016 is not a leap year. ";
echo '<br/>';
echo checkLeapYr(2017) ? "2017 is a leap year." : "2017 is not a leap year. ";
?>

Output of the above code -

2016 is a leap year.
2017 is not a leap year.