PHP Migrating 8.2 to 8.3

// Typed class constants
// Include class, trait, interface, enum
trait TestTrait {
    final protected const string TEST = 'test';
}
interface TestInterface {
    public const string TEST = 'test';
}
enum TestEnum: string {
    public const string TEST = 'test';
}

// Similar to return types, class constant types can also be "narrowed", or kept the same in a sub-class or an implementation. This follows LSP.
class ParentClass {
    public const string|int VALUE = 'MyValue';
}
class ChildClass extends ParentClass {
    public const string VALUE = 'MyValue';
}

json_validate('[1, 2, 3]'); // true
json_validate('{1, 2, 3]'); // false

// Dynamic class constant and Enum member fetch support
class Foo {
    const PHP = 'PHP 8.3';
}
$searchableConstant = 'PHP';
echo constant(Foo::class . "::{$searchableConstant}");
echo Foo::{$searchableConstant}; // instead of `constant()`

// Random extension
// public function getFloat(
//         float $min, float $max,
//         \Random\IntervalBoundary $boundary = \Random\IntervalBoundary::ClosedOpen
//     ): float
//
// enum IntervalBoundary {
//     case ClosedOpen;
//     case ClosedClosed;
//     case OpenClosed;
//     case OpenOpen;
// }
$rng = new Random\Randomizer();
echo $rng->getFloat(0, 10, \Random\IntervalBoundary::OpenOpen); // 6.7810757668383

// Generate a random number in the range 0 <= and < 1:
$rng = new Random\Randomizer();
echo $rng->nextFloat(); // 0.21185336351144

// Returns a random number sequence of a requested length ($length parameter), only containing a bytes from the requested series of bytes ($string parameter).
$rng = new Random\Randomizer();
$chars = 'AEIOU';
echo $rng->getBytesFromString($chars, 1); // "E"
echo $rng->getBytesFromString($chars, 5); // "AIIEO"

// #[\Override] attribute
// PHP enforces that the targeted class method must be overriding or implementing a parent/interface method.
class ParentClass {
    protected function demo() {}
}
class ChildClass extends ParentClass {
    #[\Override]
    protected function demo() {} // ✅ 明确覆盖

    #[\Override]
    protected function demmo() {} // ❌ Fatal error (拼写错误)
}

// Pad a multibyte string to a certain length with another multibyte string
echo mb_str_pad('中国', 6, '爱', STR_PAD_RIGHT) . "\n";
echo mb_str_pad('中国', 6, '爱', STR_PAD_LEFT) . "\n";
echo mb_str_pad('中国人', 6, '爱', STR_PAD_BOTH) . "\n";
// 中国爱爱爱爱
// 爱爱爱爱中国
// 爱中国人爱爱

// Assigning a negative index n to an empty array will now make sure that the next index is n + 1 instead of 0.
$arr = [];
$arr[-5] = 'a';
$arr[] = 'b';
var_dump($arr);
// PHP8.3    →  [-5 => 'a', -4 => 'b']
// PHP <8.3  →  [-5 => 'a', 0 => 'b']