PHP Array and Map

Array

In PHP, an array is a data structure that can hold multiple values. It can be indexed (numerical keys) or associative (string keys). Arrays are created using the array() function or the shorthand [] syntax.

// Indexed array
$fruits = array("Apple", "Banana", "Cherry");

// Associative array
$person = array(
    "name" => "John",
    "age" => 30,
    "city" => "New York"
);

// Shorthand syntax
$numbers = [1, 2, 3, 4, 5];

Array Map

The array_map() function applies a callback function to each element of an array and returns a new array with the modified values.

$numbers = [1, 2, 3, 4, 5];
$squared = array_map(fn($n) => $n ** 2, $numbers);
// $squared is now [1, 4, 9, 16, 25]

Array Filter

The array_filter() function filters elements of an array using a callback function and returns a new array with the elements that pass the test.

$numbers = [1, 2, 3, 4, 5, 6];
$even = array_filter($numbers, fn($n) => $n % 2 === 0);
// $even is now [2, 4, 6]

Array Reduce

The array_reduce() function reduces an array to a single value using a callback function.

$items = [
    ['name' => 'Apple', 'price' => 1.50],
    ['name' => 'Banana', 'price' => 0.75],
    ['name' => 'Cherry', 'price' => 2.00],
];

$total = array_reduce($items, fn($carry, $item) => $carry + $item['price'], 0);
// $total is now 4.25

Spread Operator

The spread operator (...) allows you to unpack arrays into function arguments.

function sum(int ...$numbers): int
{
    return array_sum($numbers);
}
$nums = [1, 2, 3];
echo sum(...$nums);  // Outputs: 6

Array Destructuring

Array destructuring allows you to assign array values to variables in a single statement.

// Indexed array destructuring
$coordinates = [40.7128, -74.0060];
[$lat, $lng] = $coordinates;

// Named keys
$person = ['name' => 'John', 'age' => 30];
['name' => $name, 'age' => $age] = $person;