moze li mi neko reci zasto ovaj kod ne radi?

Code:

<?php 
      $books = array();
      $total_books=4;
      $m=0;
    
          
      $titles=array(array('ovde','su','elementi','niza')
                    array('ovde','su','elementi','niza'));            //izbrisao sam podatke mnogo su kabasti, oko ovog niza je sve jasno
             
             $titleValue=$_GET['titleValue'];
            
             for($i=0;$i<$total_books;$i++){
                 if(strcasecmp($titleValue,$titles[$i][0])==0) {
                    $book_title=$titles[$i][0];
                    $book_price_us=$titles[$i][1];
                    $book_price_uk=$titles[$i][2];
                    $book_isbn=$titles[$i][3];
                    $book_author=$titles[$i][4];
                    $book_year=$titles[$i][5];
                    $book_discount=$titles[$i][6];
                    $book_category=$titles[$i][7];
                    $book_description=$titles[$i][8];
                    $book_image=$titles[$i][9]; 
                    
                    $books [] = array('title' => $book_title,
                                      'USprice' => $book_price_us,
                                      'UKprice' => $book_price_uk,
                                      'isbn' => $book_isbn,
                                      'author' => $book_author,
                                      'year' => $book_year,
                                      'discount' => $book_discount,
                                      'category' => $book_category,
                                      'description' => $book_description,
                                      'image' => $book_image);                                      
                    $m++; 
                    }
                }
            
            if($book_title==""){
                    $query_match='0';
                }
                else
                    $query_match='1';
                
                header('Content-Type: text/xml');
                $dom=new DOMDocument();
                $response=$dom->createElement('response');//root
                $dom->appendChild($response);
                
                $books=$dom->createElement("books");
                $response->appendChild($books);
                

                foreach( $books as $book )
                      {
                      $b = $dom->createElement( "book" );
                      
                      $title = $dom->createElement( 'title' );
                      $title->appendChild(
                      $dom->createTextNode( $book['title'] )
                      );
                      $b->appendChild( $title );
                      
                      $USprice = $dom->createElement( "USprice" );
                      $USprice->appendChild(
                      $dom->createTextNode( $book['USprice'] )
                      );
                      $b->appendChild( $USprice );
                      
                      $UKprice = $dom->createElement( "UKprice" );
                      $UKprice->appendChild(
                      $dom->createTextNode( $book['UKprice'] )
                      );
                      $b->appendChild( $UKprice );
                      
                      $isbn = $dom->createElement( "isbn" );
                      $isbn->appendChild(
                      $dom->createTextNode( $book['isbn'] )
                      );
                      $b->appendChild( $isbn );
                      
                      $author = $dom->createElement( "author" );
                      $author->appendChild(
                      $dom->createTextNode( $book['author'] )
                      );
                      $b->appendChild( $author );
                      
                      $year = $dom->createElement( "year" );
                      $year->appendChild(
                      $dom->createTextNode( $book['year'] )
                      );
                      $b->appendChild( $year );
                      
                      $discount = $dom->createElement( "discount" );
                      $discount->appendChild(
                      $dom->createTextNode( $book['discount'] )
                      );
                      $b->appendChild( $discount );
                      
                      $category = $dom->createElement( "category" );
                      $category->appendChild(
                      $dom->createTextNode( $book['category'] )
                      );
                      $b->appendChild( $category );
                      
                      $description = $dom->createElement( "description" );
                      $description->appendChild(
                      $dom->createTextNode( $book['description'] )
                      );
                      $b->appendChild( $description );
                      
                      $image = $dom->createElement( "image" );
                      $image->appendChild(
                      $dom->createTextNode( $book['image'] )
                      );
                      $b->appendChild( $image );
                      
                      $books->appendChild( $b );
                      }
                      
                $match=$dom->createElement('match');
                $matchText=$dom->createTextNode($query_match); 
                $match->appendChild($matchText);
                
                $number_of_matches=$dom->createElement('number_of_matches');
                $number_of_matches_text=$dom->createTextNode($m);
                $number_of_matches->appendChild($number_of_matches_text);
                      
                $books->appendChild($match);
                $books->appendChild($number_of_matches);
                
                $xmlString=$dom->saveXML();
                echo $xmlString;
                
    ?>

Code:

 $response->appendChild($books);

Code:

$books = array();

Code:

$books=$dom->createElement("books");