how to read or get the data of xsi: type of an xml

Good morning, how can I get the data or the information of an xsi: type please I'm already looking for better if it's php code please

<Discount xsi:type="ProgressivePromotion" from="2018-04-10T00:00:00" to="2018-04-14T00:00:00" type="Percent" value="50" name="Special Deal"/>