正在尝试从API输出解析XML/JSON

好。。。我使用的是PHP 5（要温和，仍在学习PHP）。CURL已启用。试图将API的XML或JSON输出加载到对象，但什么也没发生。当我手动执行有问题的URL时，我得到了我所期望的。

这是我的代码：

class XmlToJson {
    public function Parse ($url) {
        $fileContents = file_get_contents($url);
        $fileContents = str_replace(array("'n", "'r", "'t"), '', $fileContents);
        $fileContents = trim(str_replace('"', "'", $fileContents));
        $simpleXml = simplexml_load_string($fileContents);
        $json = json_encode($simpleXml);
        return $json;
    }
}
$_MySQLServer = "localhost";
$_MySQLServerUserName = "";
$_MySQLServerPassword = "";
$_MySQLDatabaseName = "";
$_SSActiveWear_UserID = "*****";
$_SSActiveWear_APIKey = "*****";
$_SSActiveWear_APIBaseURL = "https://*****/v2";
$_CategoryURL = "/categories/";
$_StylesURL = "/styles/";
$_ProductsURL = "/products/";
$_SpecsURL = "/specs/";
$_SSActiveWear_MediaType = "xml";
//$_conn = mysqli_connect($_MySQLServer, $_MySQLServerUserName, $_MySQLServerPassword, $_MySQLDatabaseName);
//Insert or Update Categories
$_URL = $_SSActiveWear_APIBaseURL . $_CategoryURL;
$_URL = $_URL . "?mediatype=$_SSActiveWear_MediaType&UserName=$_SSActiveWear_UserID&Password=$_SSActiveWear_APIKey";
$OBJ = simplexml_load_string($_URL);
print_r($OBJ);

我做错了什么？

编辑1

添加了以下代码：

$xml = simplexml_load_file($_URL) or die("Error: Cannot create object");
print_r($xml);

然后它就死了。这是否意味着代码有问题？