解析器错误:期望开始标记,找不到"<"

我是第一次使用PHP.我正在使用php示例在ebay沙箱上上传图片.我在运行PHP文件时收到以下错误:

PHP Warning:  simplexml_load_string(): Entity: line 1: parser error : Start tag expected, '<' not found in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 69
PHP Warning:  simplexml_load_string(): HTTP/1.1 200 OK in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 69
PHP Warning:  simplexml_load_string(): ^ in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 69
PHP Notice:  Trying to get property of non-object in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 92
PHP Notice:  Trying to get property of non-object in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 93
PHP Notice:  Trying to get property of non-object in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 93
PHP Notice:  Trying to get property of non-object in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 94
PHP Notice:  Trying to get property of non-object in /home/nish/stuff/market place/test/php5/UploadImage/UploadSiteHostedPictures.php on line 94

相关的是:

69. $respXmlObj = simplexml_load_string($respXmlStr);     // create SimpleXML object from string for easier parsing
                                                      // need SimpleXML library loaded for this

92. $ack        = $respXmlObj->Ack;
93. $picNameOut = $respXmlObj->SiteHostedPictureDetails->PictureName;
94. $picURL     = $respXmlObj->SiteHostedPictureDetails->FullURL;

我能理解的是respXMLObj没有正确设置.我已经检查过启用了simleXML支持.

请有人帮我调试一下.谢谢