XML / PHP getting field names

Hi all,
Im a newbe to this forum. Can anyone help.

I need to get all the field names from an xml feed and i cant find the solution anywhere.

Basicaly if i have an xml file like this but with many mor deals:

<deals>
<deal>
<dealname></dealname>
<retailername></retailername>
<tariff>
<network></network>
<tariffname></tariffname>
<lineRental></lineRental>
</tariff>
<tariff>
<network></network>
<tariffname></tariffname>
<lineRental></lineRental>
</tariff>
</deal>
</deals>

I want to simply loop through all the deals in the file and get the headings into a coma delimited varible.

dealname, retailername, tariff>network ,tariff>tariffname ,tariff>linerental, tariff2>network ,tariff2>tariffname ,tariff2>linerental

has anyone got any ide how i can do it.
I need to develop a script which will read in any xml file get the fields, map the fields to a database and store in a table then run a script which imports the xml into the database.

I've tried everything.

Thats what i have been using.
I've look and look but still cant find a simple fuction which will get the names