php写xml, 赋值由数组怎么弄

<?php



 //Creates XML string and XML document using the DOM

 $dom = new DomDocument('1.0');

 

 //add root - <books>

 $books = $dom->appendChild($dom->createElement('books'));

 

 //add <book> element to <books>

 $book = $books->appendChild($dom->createElement('book'));

 

 //add <title> element to <book>

 $title = $book->appendChild($dom->createElement('title'));

 

 //add <title> text node element to <title>

 $title->appendChild($dom->createTextNode('Great American

 Novel'));

 

 //generate xml

 $dom->formatOutput = true; // set the formatOutput attribute of

 domDocument to true

 // save XML as string or file

 $test1 = $dom->saveXML(); // put string in test1

 $dom -> save('test1.xml'); // save as file

 ?>

  <?xml version="1.0"?>

 <books>

 <book>

 <title>Great American Novel</title>

 </book>

 </books>