simple PHP script

Need a simple PHP script (web service) that will be serving up records from an XML file. The XML file contains records. Each record looks like this: <sponsor> <id>1</id> <weight>10</weight> <iPhone_banner>[login to view URL]</iPhone_banner> <BB_banner>[login to view URL]</BB_banner> <Link>[login to view URL]</Link> </sponsor> The PHP script should read the file, and return one record in XML format. The record should be chosen based on the <weight> tag. So if the <weight> value is 10, then this record should be chosen 10% of the time. If it is 60, then it should be chosen 60% of the time. The XML file is called [login to view URL], a sample of it is attached. I must be able to add records to [login to view URL] and the PHP script should still work fine.