如何以text / xml生成Restful响应？

I'm new to Restful with PHP. I have a data stored in an array as name,id . I need to produce this data to the user as xml. I'm getting my data back however is not in proper xml format.

Here is the array:

$this->books = array("Math"=>174,
                      "Music"=>874,
                      "Computing"=>348);

Here is the method that return the results:

//   /Books 
protected function Books($args){
            header("content-type: text/xml");
            if( count($args) == 0 && $this->method == "GET"){

                $dom = new DomDocument();
                $root = $dom->createElement("Books");
                $dom->appendChild($root);
                foreach($this->books as $key => $val){

                    $b = $dom->createElement("book");
                    $root->appendChild($b);

                    $bName =  $dom->createElement("name", $key);
                    $b->appendChild($bName);
                    $bID =  $dom->createElement("ID", $val);
                    $b->appendChild($bID);
                }

                $myXML= $dom->saveXML(); 
                return $myXML;
        }

The result is shown as XML, however is not well formatted:

<?xml version=\"1.0\"?>

<Books>
    <book>
        <name>Math<\/name>
            <ID>174<\/ID><\/book>
                <book>
                    <name>Music<\/name>
                        <ID>874<\/ID><\/book>
                             <book>
                                 <name>Computing<\/name>
                                    <ID>348<\/ID><\/book><\/Books>
"

Can anyone help me how to produce it in well-formed XML? why I'm getting \ before each / ? Why there is a ?