In need to speed up this code that filters the data of XML using XMLReader

Question

I am using XMLReader and avoided SimpleXML because I must handle a huge file and for memory issues, SimpleXML is not the ideal solution. However, even I coded the below script in SimpleXML, it gives me the result really much faster.

Because speed and memory is a must for this project, is there any way to speed up this code? What it does, it filters the books and show those that contains the word jQuery.

error_reporting(~0);
$xml = <<<EOD
<?xml version="1.0" encoding="ISO-8859-1"?>
<library>
 <book isbn="781">
 <name>SCJP 1.5</name>
 <info>Sun Certified Java Programmer book</info>
 </book>
 <book isbn="194">
 <name>jQuery is Awesome!</name>
 <info>jQuery Reference Book</info>
 </book> 
 <book isbn="199">
 <name>jQuery 101</name>
 <info>All you need to know about jQuery</info>
 </book> 
</library>
EOD;
$file = 'data://text/plain;base64,'.base64_encode($xml);
class XMLBookIterator implements iterator
{
 private $file;
 private $reader;
 private $state;
 private $key = 0;
 private $book;
 private $valid;
 public function __construct($file)
 {
 $this->file = $file;
 }
 public function current()
 {
 return $this->book;
 }
 public function key()
 {
 return $this->key;
 }
 public function next()
 {
 $reader = $this->reader;
 while ($next = $reader->read())
 {
 switch ($reader->nodeType)
 {
 case (XMLREADER::ELEMENT):
 $case = $reader->localName.'|'.$this->state;
 switch($case)
 {
 case 'library|0':
 break;
 case 'book|1':
 $this->book = new stdClass;
 $this->book->isbn = $reader->getAttribute('isbn'); 
 break;
 case 'name|2':
 $this->book->name = $reader->readInnerXML();
 break;
 case 'info|3':
 $this->book->info = $reader->readInnerXML();
 $this->state=0;
 break;
 default:
 throw new Exception(sprintf('Invalid State: %s.', $case));
 }
 $this->state++;
 if ($this->state === 1) break 2;
 }
 }
 $this->valid = $next;
 $this->key++;
 }
 public function rewind()
 {
 if ($this->reader) $this->reader->close();
 $this->reader = new XMLReader();
 $this->reader->open($this->file);
 $this->state = 0;
 $this->next(); // move to first element or invalidate
 if ($this->valid) $this->next(); // get first book
 $this->key = 0;
 }
 public function valid()
 {
 return $this->valid;
 }
}
class BookFilterIterator extends FilterIterator
{
 private $term;
 public function __construct($iterator, $term)
 {
 parent::__construct($iterator);
 $this->term = $term;
 }
 public function accept() {
 $book = parent::current();
 $name = $book->name;
 return false !== stripos($name, $this->term);
 }
}
// filtered books:
$books = new XMLBookIterator($file);
$filtered = new BookFilterIterator($books, 'jQuery');
foreach($filtered as $key => $book)
{
 echo 'book (', $key, '):', "\n";
 print_r($book);
}

Answer 1

Your code seems quite tidy and easy to understand, congratulations. But maybe you can check for built in functionality. XPath can search items for you:

http://www.php.net/manual/en/simplexmlelement.xpath.php
http://www.w3schools.com/xpath/xpath_syntax.asp