PHP Arrays

<?php
$cars = ["Volvo", "BMW"];
$cars[] = "Ford";
echo count($cars), "\n";
echo $cars[1], "\n";

$person = ["name" => "Ada", "age" => 36];
$person["city"] = "London";
echo $person["name"], " lives in ", $person["city"], "\n";
echo json_encode($person), "\n";

$nums = [5, 2, 9, 1];
sort($nums);
echo implode(",", $nums), "\n";
echo implode(",", array_map(fn($n) => $n * 2, $nums)), "\n";
echo implode(",", array_filter($nums, fn($n) => $n > 2)), "\n";
echo array_sum($nums), "\n";
var_dump(in_array(9, $nums));
var_dump(array_key_exists("age", $person));

3
BMW
Ada lives in London
{"name":"Ada","age":36,"city":"London"}
1,2,5,9
2,4,10,18
5,9
17
bool(true)
bool(true)