Will php be nested?

Can php be nested? If I have two. php files, one of which is & lt ;? Phprequire_once ('login. php ');? & Gt; the other login. php file is & lt ;? Phpecho 'helloworld ';? & Gt; in this way, the code in the first. php file is actually two layers. can php be nested?
If I have two. php files, one of which is
Require_once ('login. php ');
?>
In another login. php file
Echo 'hello world ';
?>
In this way, the code in the first PHP file is actually two layers. Is there a problem with this stuff?

------ Solution --------------------
This will not cause problems, and it is necessary to do so!

The actual action of require is
Generated?>
Load files
Generate
------ Solution --------------------
It's okay ..
------ Solution --------------------
Require_once ('login. php ');
?>
In another login. php file
Echo 'hello world ';
?>

==>
Require_once ('login. php'); his role is to put the login. php content (of course, there is no such content ). ) Are written to the current php file, and then executed together.

No problems.