Why do class modifiers work in php 7.0?

Question

PHP

protectedJudging by php.net, modifiers were privateintroduced in PHP 7.1.
I am using php version 7.0.

php -v

PHP 7.0.33-0+deb9u1 (cli) (built: Dec  7 2018 11:36:49) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.0.33-0+deb9u1, Copyright (c) 1999-2017, by Zend Technologies

But code with class methods with these modifiers does not crash with Fatal Error, but works as it should.
Why is this happening?

Answer 1

tashchemta they were brought back in php5.
in 7.1, they simply extended their action to constants.