how to get the year of a date value in php code example

Example 1: php get year

<?php echo date("Y"); ?>

Example 2: get current date from year input php

$date_input = '2003';
$date_output= date( "Y-m-d", mktime( 0, 0, 0, 1, 1, $date_input ));
//date_output = 2003-01-01