我不能在方法范围外调用php函数?

Me and my coworker entered in a argument in which she said that we could'nt call any functions outside a method scope in a controller, and I think its possible.

Today my code is in the following way:

index.php:

<?php

require_once("baseController.php");

?>


<h1>
  HERE I PROVE SOMETHING
</h1>

<?php

echo '<pre>', print_r(BaseController::aluno, 1), '<pre>';

?>

baseController.php

<?php

require_once('Aluno.php');


class BaseController{

  public static $aluno = new Aluno();

}

Aluno.php

<?php

class Aluno{

  public $nome;
  public $idade;


}

I don't really know what am I doing wrong, am I not allowed to do this? Always when I try to run the code it generates a error 500 in the console. What is happening here?