Associative Arrays in PHP

Multidimensional arrays can also be associative, for example, like this:

<?php
	$arr = [
		'user1' => [
			'name' => 'name1',
			'age'  => 31,
		],
		'user2' => [
			'name' => 'name2',
			'age'  => 32,
		],
	];
?>

Let's use this array to display, for example, the name of the second user:

<?php
	echo $arr['user2']['name']; // will output 'name2'
?>

Given the following array:

<?php
	$arr = [
		'boys'  => [1 => 'John', 2 => 'Jack', 3 => 'Ryan'],
		'girls' => [1 => 'Emma', 2 => 'Lily', 3 => 'Anna'],
	];
?>

Using this array, output the name of the first boy and the name of the second girl.

Given the following array:

<?php
	$arr = [
		[
			'name'   => 'user1',
			'age'    => 30,
			'salary' => 1000,
		],
		[
			'name'   => 'user2',
			'age'    => 31,
			'salary' => 2000,
		],
		[
			'name'   => 'user3',
			'age'    => 32,
			'salary' => 3000,
		],
	];
?>

Using this array, output the sum of the salaries of the first and third user.