Is it necessary to include a file containing a namespace?

Question

PHP

Created two classes admin.php and index.php . In the first I described the namespace, in the second I use it.
If I call require_once('admin.php'); then the namespace works without the use keyword . If I do not call, then nothing works at all.
And in the examples of the tutorial it is written as "connect via use NAMESPACE and you do not need to include a file containing a description of the namespace."
So is it necessary to include a namespace description file?

Answer 1

use is the syntactic sugar at the level of this particular file. Only to write new Admin instead of new Mycoolapp\model\Admin. Not related to include/require
include or require are required. Another thing is that usually they are not written to load classes explicitly, but are called through Autoloading