For up to php 5.4+
<?php
$current= new \DateTime();
$future = new \DateTime('+ 1 years');
echo $current->format('Y');
//For 4 digit ('Y') for 2 digit ('y')
?>
Or you can use it with one line
$year = (new DateTime)->format("Y");
If you wanna increase or decrease the year another method; add modify line like below.
<?PHP
$now = new DateTime;
$now->modify('-1 years'); //or +1 or +5 years
echo $now->format('Y');
//and here again For 4 digit ('Y') for 2 digit ('y')
?>