Fatal error: Class 'SuperUser' not found in D Не находит класс...PhpStorm И OpenServer

class SuperUser
{
    public $name;
    public $age;

    public function getName()
    {
        return $this->name;
    }

    public function setName($name)
    {
        $this->name = $name;
    }

    public function getAge()
    {
        return $this->age;
    }

    public function setAge($age)
    {
        $this->age = $age;
    }
}

class Students_2 extends SuperUser
{
public $course;

public function setCourse($course){
    $this->course = $course;
}

public function getCourse(){
    return $this->course;
}
}
$student = new Students_2;

$student->setCourse(3); 
$student->setName('Коля'); 
$student->setAge(25); 

echo $student->getCourse(); 
echo $student->getName(); 
echo $student->getAge();