Services_Ebay is an object-oriented abstraction layer for eBay's XML API. In addition to a SOAP-service, eBay provides an API, that does not follow any standards except wrapping all webservice calls and parameters in XML. This webservice still is more powerful than eBay's SOAP server and in addition has been heavily tested by real-life applications.
eBay's webservice enables you to use all of eBay's features (except bidding on items) in your own PHP applications. The features range from adding new items to managing the transaction, payment and shipping. Currently there are about 70 method calls available, all accept a range of parameters.
Services_Ebay (as of version 0.7.0) already provides wrappers for 50 methods as well as some model classes which help you working with the results from the calls.
To use this package you will need PHP5 with cURL support enabled and should be familiar with PHP5's exception handling.