Type hint in PHP function parameters and return values, properties and constants

Function parameters and return types:

array
function foo(array $bar)	PHP 5.1+	example
function foo(array $bar = null)	PHP 5.1+	example
function foo(?array $bar)	PHP 7.1+	example
function foo(): array	PHP 7.0+	example
function foo(): ?array	PHP 7.1+	example
bool
function foo(bool $bar)	PHP 7.0+	example
function foo(bool $bar = null)	PHP 7.0+	example
function foo(?bool $bar)	PHP 7.1+	example
function foo(): bool	PHP 7.0+	example
function foo(): ?bool	PHP 7.1+	example
callable
function foo(callable $bar)	PHP 5.4+	example
function foo(callable $bar = null)	PHP 5.4+	example
function foo(?callable $bar)	PHP 7.1+	example
function foo(): callable	PHP 7.0+	example
function foo(): ?callable	PHP 7.1+	example
float
function foo(float $bar)	PHP 7.0+	example
function foo(float $bar = null)	PHP 7.0+	example
function foo(?float $bar)	PHP 7.1+	example
function foo(): float	PHP 7.0+	example
function foo(): ?float	PHP 7.1+	example
int
function foo(int $bar)	PHP 7.0+	example
function foo(int $bar = null)	PHP 7.0+	example
function foo(?int $bar)	PHP 7.1+	example
function foo(): int	PHP 7.0+	example
function foo(): ?int	PHP 7.1+	example
iterable
function foo(iterable $bar)	PHP 7.1+	example
function foo(iterable $bar = null)	PHP 7.1+	example
function foo(?iterable $bar)	PHP 7.1+	example
function foo(): iterable	PHP 7.1+	example
function foo(): ?iterable	PHP 7.1+	example
object
function foo(object $bar)	PHP 7.2+	example
function foo(object $bar = null)	PHP 7.2+	example
function foo(?object $bar)	PHP 7.2+	example
function foo(): object	PHP 7.2+	example
function foo(): ?object	PHP 7.2+	example
self
function foo(self $bar)	PHP 5.0+	example
function foo(self $bar = null)	PHP 5.1+	example
function foo(?self $bar)	PHP 7.1+	example
function foo(): self	PHP 7.0+	example
function foo(): ?self	PHP 7.1+	example
static
function foo(static $bar)	never	example
function foo(static $bar = null)	never	example
function foo(?static $bar)	never	example
function foo(): static	PHP 8.0+	example
function foo(): ?static	PHP 8.0+	example
string
function foo(string $bar)	PHP 7.0+	example
function foo(string $bar = null)	PHP 7.0+	example
function foo(?string $bar)	PHP 7.1+	example
function foo(): string	PHP 7.0+	example
function foo(): ?string	PHP 7.1+	example
class names
function foo(ClassName $bar)	PHP 5.0+	example
function foo(ClassName $bar = null)	PHP 5.1+	example
function foo(?ClassName $bar)	PHP 7.1+	example
function foo(): ClassName	PHP 7.0+	example
function foo(): ?ClassName	PHP 7.1+	example
void
function foo(): void	PHP 7.1+	example
boolean, double, integer, resource
Never recognized as valid for type hinting		example

Class constants

visibility
const NAME = '...';	PHP 5.0+	example
private const NAME = '...';	PHP 7.1+	example
protected const NAME = '...';	PHP 7.1+	example
public const NAME = '...';	PHP 7.1+	example
types
const string NAME = '...';	PHP 8.3+	example

Class properties

visibility
var $name = '...';	PHP 4.3+	example
private $name = '...';	PHP 5.0+	example
protected $name = '...';	PHP 5.0+	example
public $name = '...';	PHP 5.0+	example
types
public string $name = '...';	PHP 7.4+	example
public ?string $name = '...';	PHP 7.4+	example