PHP 8.3 是 PHP 语言的主版本更新。它包含了许多新功能，
它包含了许多新功能，例如：类常量显式类型、只读属性深拷贝，以及对随机性功能的补充。一如既往，它还包括性能改进、错误修复和常规清理等。

类型化类常量

PHP < 8.3
interface I {
    // We may naively assume that the PHP constant is always a string.
    const PHP = 'PHP 8.2';
}

class Foo implements I {
    // But implementing classes may define it as an array.
    const PHP = [];
}

PHP 8.3
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

动态获取类常量

PHP < 8.3
class Foo {
    const PHP = 'PHP 8.2';
}

$searchableConstant = 'PHP';

var_dump(constant(Foo::class . "::{$searchableConstant}"));

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

$searchableConstant = 'PHP';

var_dump(Foo::{$searchableConstant});

新增 #[\Override] 属性

PHP < 8.3
use PHPUnit\Framework\TestCase;

final class MyTest extends TestCase {
    protected $logFile;

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

    protected function taerDown(): void {
        fclose($this->logFile);
        unlink('/tmp/logfile');
    }
}

// The log file will never be removed, because the
// method name was mistyped (taerDown vs tearDown).

PHP 8.3
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

通过给方法添加 #[\Override] 属性，PHP 将确保在父类或实现的接口中存在同名的方法。添加该属性表示明确说明覆盖父方法是有意为之，并且简化了重构过程，因为删除被覆盖的父方法将被检测出来。

新增 Randomizer::getBytesFromString() 方法

PHP < 8.3
// This function needs to be manually implemented.
function getBytesFromString(string $string, int $length) {
    $stringLength = strlen($string);

    $result = '';
    for ($i = 0; $i < $length; $i++) {
        // random_int is not seedable for testing, but secure.
        $result .= $string[random_int(0, $stringLength - 1)];
    }

    return $result;
}

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

echo $randomDomain;

PHP 8.3
// 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;

在 PHP 8.2 中新增的 Random 扩展 通过一个新方法生成由特定字节组成的随机字符串。这种方法可以使开发者更轻松的生成随机的标识符（如域名），以及任意长度的数字字符串。

新增 Randomizer::getFloat() 和 Randomizer::nextFloat() 方法 RFC 文档

PHP < 8.3
// Returns a random float between $min and $max, both including.
function getFloat(float $min, float $max) {
    // This algorithm is biased for specific inputs and may
    // return values outside the given range. This is impossible
    // to work around in userland.
    $offset = random_int(0, PHP_INT_MAX) / PHP_INT_MAX;

    return $offset * ($max - $min) + $min;
}

$temperature = getFloat(-89.2, 56.7);

$chanceForTrue = 0.1;
// getFloat(0, 1) might return the upper bound, i.e. 1,
// introducing a small bias.
$myBoolean = getFloat(0, 1) < $chanceForTrue;

PHP 8.3
$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;

由于浮点数的精度和隐式四舍五入的限制，在特定区间内生成无偏差的浮点数并非易事，常建的用户解决方案可能会生成有偏差的结果或超出要求范围的数字。

Randomizer 扩展了两种方法，用于随机生成无偏差的浮点数。Randomizer::getFloat() 方法使用的是 γ-section 算法，该算法发表于 Drawing Random Floating-Point Numbers from an Interval. Frédéric Goualard, ACM Trans. Model. Comput. Simul., 32:3, 2022.

#other

• PHP8.3

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