Use either date or strftime. In this case, it doesn’t matter as a year is a year, no matter what (unless there’s a locale that formats the year differently).
Example
<?php echo date("Y"); ?>
Solution 2
$now = new DateTime();
$year = $now->format("Y");
Using class member access on instantiation (php>=5.4):
$year = (new DateTime)->format("Y");
https://stackoverflow.com/questions/64003/how-do-i-use-php-to-get-the-current-year/64097#64097