New Features in PHP 8.4: A Comprehensive Guide with Code Examples

`PHP 8.4`, released in November 2024, introduces a host of powerful features and improvements that streamline development, enhance code expressiveness, and address long-standing developer requests. Here’s a detailed look at the most impactful additions, complete with code examples.

Property Hooks: Custom `Getters` and `Setters` Without Boilerplate

Property hooks allow you to define custom logic for getting and setting class properties, eliminating the need for verbose `getter` and `setter` methods. Inspired by languages like Kotlin and C#, this feature brings a more declarative way to control property access and mutation.

class User {
    public string $firstName {
        set(string $name) { $this->firstName = ucfirst($name); }
    }
    public string $lastName {
        set(string $name) => ucfirst($name);
    }
    public string $fullName {
        get => $this->firstName . ' ' . $this->lastName;
        set(string $name) {
            [$this->firstName, $this->lastName] = explode(' ', $name, 2);
        }
    }
}

$user = new User();
$user->firstName = 'ash';
$user->lastName = 'allen';
echo $user->fullName; // Ash Allen

You can also use the new `__PROPERTY__` magic constant inside hooks to reference the property name.

Asymmetric Property Visibility: Fine-Grained Control Over Read/Write

With asymmetric visibility, you can now assign different visibility levels for reading and writing a property. For example, a property can be publicly readable but only privately writable, which is especially useful for value objects and DTOs.

class Book {
    public private(set) string $title;
    public protected(set) string $author;

    public function __construct(string $title, string $author) {
        $this->title = $title;
        $this->author = $author;
    }
}

$book = new Book('PHP 8.4', 'Jane Doe');
echo $book->title; // Allowed
$book->title = 'New Title'; // Error: cannot set outside class

This syntax also works with promoted constructor properties.

New Array Functions: `array_find`, `array_find_key`, `array_any`, `array_all`

`PHP 8.4` introduces several new array functions that simplify common search and filter operations:

• `array_find($array, $callback)`: Returns the first matching element.
• `array_find_key($array, $callback)`: Returns the key of the first matching element.
• `array_any($array, $callback)`: Returns true if any element matches.
• `array_all($array, $callback)`: Returns true if all elements match.

$numbers = [1, 2, 3, 4, 5, 6];

$firstEven = array_find($numbers, fn($n) => $n % 2 === 0); // 2
$firstEvenKey = array_find_key($numbers, fn($n) => $n % 2 === 0); // 1
$hasEven = array_any($numbers, fn($n) => $n % 2 === 0); // true
$allEven = array_all($numbers, fn($n) => $n % 2 === 0); // false

Class Instantiation Without Extra Parentheses

Previously, chaining methods or accessing properties on a newly instantiated object required wrapping the new expression in parentheses. `PHP 8.4` removes this requirement, making code cleaner and more intuitive:

// Before PHP 8.4
$name = (new ReflectionClass($object))->getShortName();

// Now in PHP 8.4
$name = new ReflectionClass($object)->getShortName();

This applies to accessing methods, properties, static methods, and constants directly after `new`.

`HTML5`-Compliant `DOM` API

`PHP 8.4` introduces new `DOM` classes that are fully standards-compliant with `HTML5`, fixing several long-standing bugs and making HTML parsing more reliable. The new API is available alongside the old one for backward compatibility.

$dom = Dom\HTMLDocument::createFromString('<main><article class="featured">Hello</article></main>');
$node = $dom->querySelector('main > article.featured');
echo $node->textContent; // Hello

New Multibyte String Functions

Working with multibyte strings is easier with the addition of these functions:

• `mb_trim()`, `mb_ltrim()`, `mb_rtrim()`: Multibyte-safe trimming.
• `mb_ucfirst()`, `mb_lcfirst()`: Multibyte-safe case conversion.

$str = "  Hello  ";
echo mb_trim($str); // "Hello"
echo mb_ucfirst("hello"); // "Hello"

Other Notable Improvements

• `#[Deprecated]` AttributeMark functions, classes, or properties as deprecated using the new attribute syntax.
• Enhanced Password Hashing: The default `bcrypt` cost increased from `10` to `12` for better security.
• Expanded `HTTP` Verb Support: `$_POST` and `$_FILES` now support additional `HTTP` verbs.
• Driver-specific `PDO` Subclasses: Access driver-specific features directly from `PDO` subclasses.
• Performance and Compatibility: Updates to `JIT`, `OpenSSL`, `libcurl`, and Unicode support.

Conclusion

`PHP 8.4` is a feature-rich release that modernizes the language and reduces boilerplate. Features like property hooks, asymmetric visibility, new array utilities, and cleaner class instantiation syntax will have a significant positive impact on day-to-day development.