Can error values ​​be used as the type of function return values ​​in PHP?

PHP does allow error values ​​to be used as function return value types, using Throwable or its subclasses as the return value type, with syntax such as function_name(): Throwable {}. By making it clear that a function may throw an error or exception, the caller can handle the return value accordingly.

#Is it possible to use error value as function return value type in PHP?

In PHP, we can specify the type of function return value through type hints. But is it possible to specify an error value as the return value type?

The answer is: Yes

PHP provides a built-in Throwable type, which is the base class for all errors and exceptions. We can use Throwable or its subclasses as the function return value type to indicate that the function may throw errors or exceptions.

Syntax

function function_name(): Throwable {
    // ...
}

Practical case

Consider the following function, which fetches user data from the database. If the user does not exist, it will throw a UserNotFoundException exception:

function get_user(int $user_id): User {
    $user = $db->get_user($user_id);
    if (!$user) {
        throw new UserNotFoundException("User not found with ID $user_id");
    }

    return $user;
}

We can specify Throwable as the return value type in the function declaration to make it clear that it may An error or exception will be thrown:

function get_user(int $user_id): User|Throwable {
    $user = $db->get_user($user_id);
    if (!$user) {
        throw new UserNotFoundException("User not found with ID $user_id");
    }

    return $user;
}

Now, when the function is called, we will know that it may return a User object, or it may throw a Throwable. We can handle the return value accordingly:

try {
    $user = get_user(1);
    // 使用 $user 对象
} catch (Throwable $error) {
    // 处理错误
}

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