What new features appeared in PHP version 7.4?

• Typed class properties.
• Arrow functions (short syntax for anonymous functions).
• Null coalescing assignment operator (??=).
• Preloading for performance improvement.
• Spread operator in arrays (...).
• Weak references for memory management.
• Limited covariance and contravariance of types.
• CFI (Custom ini files) — support for user-defined ini files.
• Deprecation of some functions and features (e.g., aliases is_countable, FILTER_SANITIZE_MAGIC_QUOTES, etc.).
• Improvements in FFI (Foreign Function Interface).
• Thousands separator in numeric literals (1_000_000).

<?php

// Typed property
class User
{
    public string $name;
    public ?int $age; // Can be null
}

// Arrow function
$func = fn(int $a, int $b) => $a + $b;
echo $func(1, 2); // 3

// Null coalescing assignment operator
$data = [
    'key' => null,
];
$value ??= 'default';
echo $value; // default

// Spread operator in arrays
$arr1 = [1, 2];
$arr2 = [3, 4];
$merged = [...$arr1, ...$arr2]; // [1, 2, 3, 4]

<?php

// WeakReference
$obj = new stdClass;
$weakref = WeakReference::create($obj);

unset($obj); // Object removed

// Check
var_dump($weakref->get()); // null