What is the scope of require_once in PHP?

Question

Simple question: Is the scope of require_once global?

For example:

Answer 1

At least in PHP 7.3, require_once has global scope.
If it would not, both x.php and z.php should throw errors as y.php does:

a.php

b.php

---

x.php

-->

#0 c() called at [/var/www/b.php:2]  
#1 b() called at [/var/www/a.php:3]  
#0 c() called at [/var/www/a.php:4]  

y.php

--> Fatal error: Uncaught Error: Call to undefined function b() in /var/www/y.php on line 3

z.php

-->

#0 b() called at [/var/www/z.php:4]