Description:
------------
The documentation for the following functions include parameter type declarations:

SessionHandler::open(string $save_path, string $session_name)
SessionHandler::read(string $session_id)
SessionHandler::write(string $session_id, string $session_data)
SessionHandler::destroy(string $session_id)
SessionHandler::gc(int $maxlifetime)

http://php.net/manual/en/class.sessionhandler.php

however using the same type declarations in the session handler class returns a PHP fatal error.

Also tested with PHP 7.1.0-dev rc3495d5 with the same result.

Test script:
---------------
<?php
class SessionTest implements \SessionHandlerInterface
{
    public function __construct()
    {
        session_set_save_handler($this, true);
    }

    public function open(string $save_path, string $name): bool
    {
        return true;
    }

    public function close(): bool
    {
        return true;
    }

    public function read(string $session_id): string
    {
        return '';
    }

    public function write(string $session_id, string $session_data): bool
    {
        return true;
    }

    public function destroy(string $session_id): bool
    {
        return true;
    }

    public function gc(int $maxlifetime): bool
    {
        return true;
    }
}

$SessionTest = new SessionTest();


Expected result:
----------------
No error should be expected.

Actual result:
--------------
Fatal error: Declaration of SessionTest::open(string $save_path, string $name): bool must be compatible with SessionHandlerInterface::open($save_path, $session_name) in C:\SessionTest.php on line 2

Fatal error: Declaration of SessionTest::read(string $session_id): string must be compatible with SessionHandlerInterface::read($key) in C:\SessionTest.php on line 2

Fatal error: Declaration of SessionTest::write(string $session_id, string $session_data): bool must be compatible with SessionHandlerInterface::write($key, $val) in C:\SessionTest.php on line 2

Fatal error: Declaration of SessionTest::destroy(string $session_id): bool must be compatible with SessionHandlerInterface::destroy($key) in C:\SessionTest.php on line 2

Fatal error: Declaration of SessionTest::gc(int $maxlifetime): bool must be compatible with SessionHandlerInterface::gc($maxlifetime) in C:\SessionTest.php on line 2