PHP: Empty simpleXMLElement Object

I am trying to retrieve data from API, I managed to get the data however when I try to convert to SimpleXMLElement it returns empty object. when I change the header to Content-Type: text/XML I have the following data.

<DataSet xmlns="http://tempuri.org/">
<xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://ift.tt/tphNwY" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
<xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:UseCurrentLocale="true">
  <xs:complexType>
    <xs:choice minOccurs="0" maxOccurs="unbounded">
      <xs:element name="Table">
        <xs:complexType>
          <xs:sequence>
            <xs:element name="ITEM_CODE" type="xs:string" minOccurs="0" />
            <xs:element name="ITEM_NAME" type="xs:string" minOccurs="0" />
            <xs:element name="ITEM_TYPE" type="xs:string" minOccurs="0" />
            <xs:element name="ITEM_DESCRIPTION" type="xs:string" minOccurs="0" />
            <xs:element name="CATEGORY" type="xs:string" minOccurs="0" />
            <xs:element name="ITEM_BRAND" type="xs:string" minOccurs="0" />
            <xs:element name="ITEM_MODEL" type="xs:string" minOccurs="0" />
            <xs:element name="GROUP_NAME" type="xs:string" minOccurs="0" />
            <xs:element name="UNIT_OF_MEASURE" type="xs:string" minOccurs="0" />
            <xs:element name="ALTERNATE_LOOK_UP" type="xs:string" minOccurs="0" />
            <xs:element name="DOUBLE_WEB_PRICE" type="xs:decimal" minOccurs="0" />
            <xs:element name="IMAGEKEY" type="xs:string" minOccurs="0" />
          </xs:sequence>
        </xs:complexType>
      </xs:element>
    </xs:choice>
  </xs:complexType>
</xs:element>
</xs:schema>
  <diffgr:diffgram xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"               xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1">
<NewDataSet xmlns="">
    <Table diffgr:id="Table1" msdata:rowOrder="0" diffgr:hasChanges="inserted">
    <ITEM_CODE>item1</ITEM_CODE>
    <ITEM_NAME>item1</ITEM_NAME>
    <ITEM_TYPE>t1</ITEM_TYPE>
    <ITEM_DESCRIPTION />
    <CATEGORY />
    <ITEM_BRAND />
    <ITEM_MODEL />
    <GROUP_NAME />
    <UNIT_OF_MEASURE />
    <ALTERNATE_LOOK_UP />
    <DOUBLE_WEB_PRICE>0.0000</DOUBLE_WEB_PRICE>
  </Table>
  <Table diffgr:id="Table2" msdata:rowOrder="1" diffgr:hasChanges="inserted">
    <ITEM_CODE>item2</ITEM_CODE>
    <ITEM_NAME>item2</ITEM_NAME>
    <ITEM_TYPE />
    <ITEM_DESCRIPTION />
    <CATEGORY />
    <ITEM_BRAND />
    <ITEM_MODEL />
    <GROUP_NAME />
    <UNIT_OF_MEASURE />
    <ALTERNATE_LOOK_UP />
    <DOUBLE_WEB_PRICE>0.0000</DOUBLE_WEB_PRICE>
  </Table>
  <Table diffgr:id="Table3" msdata:rowOrder="2" diffgr:hasChanges="inserted">
    <ITEM_CODE>item3</ITEM_CODE>
    <ITEM_NAME>item3</ITEM_NAME>
    <ITEM_TYPE />
    <ITEM_DESCRIPTION />
    <CATEGORY />
    <ITEM_BRAND />
    <ITEM_MODEL />
    <GROUP_NAME />
    <UNIT_OF_MEASURE />
    <ALTERNATE_LOOK_UP />
    <DOUBLE_WEB_PRICE>0.0000</DOUBLE_WEB_PRICE>
  </Table>
  <Table diffgr:id="Table4" msdata:rowOrder="3" diffgr:hasChanges="inserted">
    <ITEM_CODE>item4</ITEM_CODE>
    <ITEM_NAME>item4</ITEM_NAME>
    <ITEM_TYPE />
    <ITEM_DESCRIPTION />
    <CATEGORY />
    <ITEM_BRAND />
    <ITEM_MODEL />
    <GROUP_NAME />
    <UNIT_OF_MEASURE />
    <ALTERNATE_LOOK_UP />
    <DOUBLE_WEB_PRICE>0.0000</DOUBLE_WEB_PRICE>
  </Table>

How can I get the data?