Explicit Key Specification in PHP

If necessary, keys can be specified explicitly:

<?php
	$arr = []; // create an empty array
	
	$arr[0] = 'a'; // add element 'a' to key 0
	$arr[1] = 'b'; // add element 'b' to key 1
	$arr[2] = 'c'; // add element 'c' to key 2
	
	var_dump($arr); // will output ['a', 'b', 'c']
?>

Keys can be not only numeric, but also string:

<?php
	$arr = [];
	
	$arr['a'] = 1;
	$arr['b'] = 2;
	$arr['c'] = 3;
	
	var_dump($arr); // will output ['a' => 1, 'b' => 2, 'c' => 3]
?>

Given an empty array:

<?php
	$arr = [];
?>

Using the described method, write the current year to the key 'year', the current month to the key 'month', and the current day to the key 'day'.