CascadiaPHP 2024

Never

never is a return-only type indicating the function does not terminate. This means that it either calls exit(), throws an exception, or is an infinite loop. Therefore, it cannot be part of a union type declaration. Available as of PHP 8.1.0.

never is, in type theory parlance, the bottom type. Meaning it is the subtype of every other type and can replace any other return type during inheritance.

add a note

User Contributed Notes 2 notes

up
19
ali1289445 at gmail dot com
1 year ago
<?php

function sayHello(string $name): never
{
echo
"Hello, $name";
exit();
// if we comment this line, php throws fatal error
}

sayHello("John"); // result: "Hello, John"
up
-14
mateusz dot charytoniuk at protonmail dot com
1 year ago
Overriding the return type of native interfaces:

<?php

class ReadonlyArrayAccess implements ArrayAccess
{
public function
__construct(private readonly $array) {}

public function
offsetExists(mixed $offset): bool
{
return isset(
$this->array[$offset]);
}

public function
offsetGet(mixed $offset): mixed
{
return
$this->array[$offset];
}

public function
offsetSet(mixed $offset, mixed $value): never
{
throw new
LogicException('This array is read only');
}

public function
offsetUnset(mixed $offset): never
{
throw new
LogicException('This array is read only');
}
}
To Top