Authorization in header not set

hello,
I am new in directadmin,when I send a request to a php page with "Authorizaion" header it seems it don't Authorizaion but when I try to send another things in header it works well.
Is there any limitation for Authorization in Directadmin ?

here is my codes:

if(isset($_SERVER['HTTP_AUTHORIZATION'])){ echo "Authorization is set";
}else{ echo "Authorization is not set";
}