php中的自动加载错误

Question

I am trying autoload function in php. The files are all in the same directory. I have a file called aviation.php with the following code:

class Avaitor{

    public function __construct(){

        echo "Fly high<br>";
    }
}

Then in my autoloader file I am trying to do this:

function __autoload($fileName){

    if(file_exists($fileName . ".php"))
        require_once $fileName . ".php"; 

}

//require_once "aviatior.php";
$pilot = new Avaitor();

But I am getting this error:

Fatal error: Uncaught Error: Class 'Avaitor' not found in /Applications/MAMP/htdocs/php_oop/autoload.php:22 Stack trace: #0 {main} thrown in /Applications/MAMP/htdocs/php_oop/autoload.php on line 22

Just to test that require_once does find my aviator.php I tried it out and then commented it out.

What am I doing wrong here?