Explore PHP 8.3: Typed Class Constants, Readonly Clone, and New Randomizer APIs

Introduction

PHP 8.3 is a major release of the PHP language that adds many new features, performance improvements, bug fixes, and general clean‑ups.

Typed Class Constants

interface I {
    const string PHP = 'PHP 8.3';
}

class Foo implements I {
    const string PHP = [];
}
// Fatal error: Cannot use array as value for class constant
// Foo::PHP of type string

Class constants can now be declared with explicit types, and assigning a value of a mismatched type triggers a fatal error.

Dynamic Access to Class Constants

class Foo {
    const PHP = 'PHP 8.3';
}

$searchableConstant = 'PHP';
var_dump(Foo::{$searchableConstant});

Constants can be accessed dynamically using a variable that holds the constant name.

New #[\Override] Attribute

use PHPUnit\Framework\TestCase;

final class MyTest extends TestCase {
    protected $logFile;

    protected function setUp(): void {
        $this->logFile = fopen('/tmp/logfile', 'w');
    }

    #[\Override]
    protected function taerDown(): void {
        fclose($this->logFile);
        unlink('/tmp/logfile');
    }
}
// Fatal error: MyTest::taerDown() has #[\Override] attribute, but no matching parent method exists

Adding the #[\Override] attribute tells PHP to ensure a method with the same name exists in a parent class or interface, helping catch accidental mismatches during refactoring.

Readonly Property Deep Clone

class PHP {
    public string $version = '8.2';
}

readonly class Foo {
    public function __construct(public PHP $php) {}

    public function __clone(): void {
        $this->php = clone $this->php;
    }
}

$instance = new Foo(new PHP());
$cloned = clone $instance;
$cloned->php->version = '8.3';

The readonly attribute now permits a single modification inside __clone , enabling deep cloning of readonly properties.

New json_validate() Function

var_dump(json_validate('{ "test": { "foo": "bar" } }')); // true

json_validate() checks whether a string is syntactically valid JSON, offering a more efficient alternative to json_decode() when only validation is needed.

Randomizer Enhancements

Randomizer::getBytesFromString()

// A \Random\Engine may be passed for seeding,
// the default is the secure engine.
$randomizer = new \Random\Randomizer();

$randomDomain = sprintf(
    "%s.example.com",
    $randomizer->getBytesFromString('abcdefghijklmnopqrstuvwxyz0123456789', 16),
);

echo $randomDomain;

This new method generates a random string composed of a specific number of bytes, useful for creating identifiers such as domain names.

Randomizer::getFloat() and Randomizer::nextFloat()

$randomizer = new \Random\Randomizer();

$temperature = $randomizer->getFloat(
    -89.2,
    56.7,
    \Random\IntervalBoundary::ClosedClosed,
);

$chanceForTrue = 0.1;
// Randomizer::nextFloat() is equivalent to
// Randomizer::getFloat(0, 1, \Random\IntervalBoundary::ClosedOpen).
// The upper bound, i.e. 1, will not be returned.
$myBoolean = $randomizer->nextFloat() < $chanceForTrue;

Generating unbiased floating‑point numbers within a specific interval is non‑trivial; these methods provide reliable, boundary‑aware random floats.

New Classes, Interfaces, and Functions

DOMElement::getAttributeNames(), ::insertAdjacentElement(), ::insertAdjacentText(), ::toggleAttribute()

DOMNode::contains(), ::getRootNode(), ::isEqualNode()

DOMNameSpaceNode::contains()

DOMParentNode::replaceChildren()

IntlCalendar::setDate(), ::setDateTime()

IntlGregorianCalendar::createFromDate(), ::createFromDateTime()

ldap_connect_wallet() and ldap_exop_sync()

mb_str_pad()

posix_sysconf(), posix_pathconf(), posix_fpathconf(), posix_eaccess()

ReflectionMethod::createFromMethodName()

socket_atmark()

str_increment(), str_decrement(), stream_context_set_options()

ZipArchive::getArchiveFlag()

Support for custom EC parameters in OpenSSL extension

INI setting zend.max_allowed_stack_size to control maximum stack size

Deprecations and Backward‑Incompatible Changes

More appropriate Date/Time exceptions

Negative index handling in empty arrays now yields n + 1 instead of 0 Changes to range() behavior

Changes to redeclaring static properties in traits

Constant U_MULTIPLE_DECIMAL_SEPERATORS renamed to U_MULTIPLE_DECIMAL_SEPARATORS Mt19937 variant MT_RAND_PHP deprecated ReflectionClass::getStaticProperties() no longer returns empty

INI directives assert.active, assert.bail, assert.callback, assert.exception, assert.warning deprecated

Calling get_class() or get_parent_class() without arguments deprecated