I have the followng XML file from Ebay

<GeteBayDetailsResponse xmlns="urn:ebay:apis:eBLBaseComponents"><Timestamp>2012-07-04T12:02:14.541Z</Timestamp><Ack>Success</Ack><Version>779</Version><Build>E779_INTL_BUNDLED_14986004_R1</Build><SiteDetails><Site>US</Site><SiteID>0</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Canada</Site><SiteID>2</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>UK</Site><SiteID>3</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Germany</Site><SiteID>77</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Australia</Site><SiteID>15</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>France</Site><SiteID>71</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>eBayMotors</Site><SiteID>100</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Italy</Site><SiteID>101</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Netherlands</Site><SiteID>146</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Spain</Site><SiteID>186</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>India</Site><SiteID>203</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>HongKong</Site><SiteID>201</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Singapore</Site><SiteID>216</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Malaysia</Site><SiteID>207</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Philippines</Site><SiteID>211</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>CanadaFrench</Site><SiteID>210</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Poland</Site><SiteID>212</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Belgium_Dutch</Site><SiteID>123</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Belgium_French</Site><SiteID>23</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Austria</Site><SiteID>16</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Switzerland</Site><SiteID>193</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><SiteDetails><Site>Ireland</Site><SiteID>205</SiteID><DetailVersion>1</DetailVersion><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></SiteDetails><UpdateTime>2009-07-09T10:48:17.000Z</UpdateTime></GeteBayDetailsResponse>

I need to get the value of node SiteID where the node Site matches whatever variable I pass. The code I have is:

$xml_file ='SiteDetails.xml';
    $xmlDoc = new DomDocument();
    $xmlDoc->load($xml_file);
    $xpath = new DOMXpath($xmlDoc);

    $siteIDList =  $xpath->query("/GeteBayDetailsResponse/SiteDetails[Site=$site]/SiteID");

    var_dump($siteIDList);
    echo $siteIDList->SiteID;

I get the following result:

object(DOMNodeList)#11 (0) {
}

Can anyone help? I want to get a value of 3.