XML problems inserrecord potential

I think this is mostly due to the fact that I am unfamiliar with XML and this particular notion of PHP cURL.

When I write the XML, do I have to input all the fields or just the ones marked as necessary. For example

the oppurtunity has (accountID, ContactID,oppurtunityName, date Due, Mailing) and lets so I didnt want to add mailing, does <fl val="mailing"> still need to be there?

I ask this because I just did this:
<?xml version="1.0" encoding="UTF-8" ?>
<Potentials>
    <row no="1">
        <FL val="ACCOUNTID">accountID is in here</FL>
        <FL val="Potential Name">Potential Name is in here</FL>
        <FL val="Stage">"Perdu"</FL>
        <FL val="Closing Date">01/04/2009</FL>
    </row>
</Potentials>

and in php

$query = "newFormat=1&authtoken={$authtoken}&scope=crmapi&xmlData={$xmlData->asXML()}";

   $ch = curl_init();
    /* set url to send post request */
    curl_setopt($ch, CURLOPT_URL, $url);
    /* allow redirects */
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
    /* return a response into a variable */
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    /* times out after 30s */
    curl_setopt($ch, CURLOPT_TIMEOUT, 30);
    /* set POST method */
    curl_setopt($ch, CURLOPT_POST, 1);
    /* add POST fields parameters */
curl_setopt($ch, CURLOPT_POSTFIELDS, $query);// Set the request as a POST FIELD for curl.
//Execute cUrl session
$response = curl_exec($ch);
curl_close($ch);
echo $response;

and it used to return errors, now after a fixes it returns nothing and the oppurtunity is not created

any help would be greatly appreciated

Thank you