The new version of PHP: PHP 8, what is new and exciting about it?

New features of PHP 8

Union types and the `mixed` type

• class (PHP 5)
• self (PHP 5)
• array (PHP 5.1)
• callable (PHP 5.4)
• bool (PHP 7)
• float (PHP 7)
• int (PHP 7)
• string (PHP 7)
• iterable (PHP 7.1)
• object (PHP 7.2)

Named arguments

// PHP 7
htmlspecialchars($string, ENT_COMPAT | ENT_HTML401, 'UTF-8', false);

// PHP 8
htmlspecialchars($string, double_encode: false);

use App\Attributes\ExampleAttribute;

#[ExampleAttribute]
class Foo
{
    #[ExampleAttribute]
    public const FOO = 'foo';
 
    #[ExampleAttribute]
    public $x;
 
    #[ExampleAttribute]
    public function foo(#[ExampleAttribute] $bar) { }
}



#[Attribute]
class ExampleAttribute
{
    public $value;
 
    public function __construct($value)
    {
        $this->value = $value;
    }
}

Constructor property promotion

// PHP 7
class Point {
	public float $x;
	public float $y;
 
	public function __construct(
    		float $x = 0.0,
    		float $y = 0.0,
	) {
    		$this->x = $x;
    		$this->y = $y;	
}
}

// PHP 8
class Point {
	public function __construct(
    		public float $x = 0.0,
    		public float $y = 0.0,
	) {
		//
	}
}

Added match expression

switch (1) {
	case 0:
    	$result = 'Foo';
    	break;
	case 1:
    	$result = 'Bar';
    	break;
	case 2:
    	$result = 'Baz';
    	break;
}
 
echo $result;

// PHP 8
echo match (1) {
	0 => 'Foo',
	1 => 'Bar',
	2 => 'Baz',
};

Added nullsafe operator

// PHP 7
$country =  null;
 
if ($session !== null) {
	$user = $session->user;
 
	if ($user !== null) {
    	$address = $user->getAddress();
 
    	if ($address !== null) {
        	$country = $address->country;
    	}
	}
}

// PHP 8
$country = $session?->user?->getAddress()?->country;

Allowing `::class` on objects

New `Stringable` interface

Abstract trait method validation

trait T
{
	abstract public function test(): string;
}

class C
{
	use T;

	public function test() // Allowed in PHP 7
	{
    		//
	}

	public function test(): int // Forbidden in PHP 8
	{
    		//
	}

	public function test(): string // Allowed in PHP 8
	{
    		//
	}
}

Non-capturing catches

        try {
            //
        } catch (Exception $exception){ // Unused variable
            //
        }

        try {
            //
        } catch (Exception){
            //
        }

Ensure correct signatures of magic methods

New `str_contains`, `str_starts_with` and `str_ends_with` functions

Weak maps

$map = new WeakMap;
$obj = new stdClass;
$map[$obj] = 42;

var_dump($map);
// object(WeakMap)#1 (1) {
//   [0]=>
//   array(2) {
//     ["key"]=>
//     object(stdClass)#2 (0) {
//     }
//     ["value"]=>
//     int(42)
//   }
// }
 
// The object is destroyed here, and the key is automatically removed from the weak map.
unset($obj);
var_dump($map);
// object(WeakMap)#1 (0) {
// }

Changes

Performance improvements with the PHP 8 JIT compiler

JIT makes bench.php more than two times faster: 0.140 sec vs 0.320 sec. It is expected to make most CPU-intensive workloads run significantly faster.
According to Nikita, PHP-Parser became ~1.3 times faster with JIT. Amphp hello-world.php got just 5% speedup.
However, like the previous attempts - it currently doesn't seem to significantly improve real-life apps like WordPress (with opcache.jit=1235 326 req/sec vs 315 req/sec).
It's planned to provide additional effort, improving JIT for real-life apps, using profiling and speculative optimizations.

Breaking Changes

Conclusion of PHP 8

Should I upgrade to PHP 8?

References

• https://stitcher.io/blog/jit-in-real-life-web-applications
• https://stitcher.io/blog/new-in-php-8
• https://wiki.php.net/rfc/jit
• https://github.com/php/php-src/blob/PHP-8.0/UPGRADING#L20
• https://stitcher.io/blog/php-jit
• Release 26 November https://wiki.php.net/todo/php80