[jQuery] how can I call php function in jquery ?

[dziobacz]

I have in PHP file ajax.php:
class Data
{

        public function __construct()
        {
                ....................
        }

        public function select($idl)
        {
                ....................
        }

        public function delete($id)
        {
                .....................
        }
}


My jquery function looks now:
function deleteComment(id)
{
        $.post("ajax.php",
                {

                },
                function(data) {
                    ...........
                }
        );
}

How can I in function deleteComment(id) call php function delete($id)
from file ajax.php ?