What new features appeared in PHP 7.4?

• Introduction of typed class properties.
• Addition of arrow functions (short syntax for lambda functions).
• Null coalescing assignment operator (??=).
• Adding WeakReference.
• Preloading for improved application performance.
• Covariance of return types and contravariance of function arguments.
• Spread operator (...) syntax in array expressions.
• unserialize() now throws Throwable.
• Performance improvements, especially in FFI (Foreign Function Interface).
• Deprecation of some features.

<?php

// Example of a typed property
class User
{
    public int $id;
    public string $name;
}

// Example of an arrow function
$numbers = [1, 2, 3, 4];
$squared = array_map(fn($n) => $n * $n, $numbers);

// Example of null coalescing assignment operator
$data = ['value' => null];
$data['value'] ??= 'default'; // $data['value'] will become 'default'

// Example of spread operator in arrays
$array1 = [1, 2];
$array2 = [3, 4];
$merged = [...$array1, ...$array2]; // $merged will be [1, 2, 3, 4]