How to trace URLloader request

Hello,

Is it possible to have a trace statement from a urlloader request that is being sent to a PHP file?, i want to see the url as it is being sent, but all i am able to get at this point is just the variable being sent indiviually. I tried these

trace("PHP request sent to server " + loader.load(request));
trace("PHP request sent to server " + loader);

and i gives me these traces:

PHP request sent to server undefined
PHP request sent to server [object URLLoader]