PHPでXML形式のファイルを読み取る方法

<books>
<book>
<author>Jack Herrington</author>
<title>PHP Hacks</title>
<publisher>O&#39;Reilly</publisher>
</book>
<book>
<author>Jack Herrington</author>
<title>Podcasting Hacks</title>
<publisher>O&#39;Reilly</publisher>
</book>
</books>

<?php
$doc = new DOMDocument();
$doc->load( &#39;books.xml&#39; );
$books = $doc->getElementsByTagName( "book" );
foreach( $books as $book )
{
$authors = $book->getElementsByTagName( "author" );
$author = $authors->item(0)->nodeValue;
$publishers = $book->getElementsByTagName( "publisher" );
$publisher = $publishers->item(0)->nodeValue;
$titles = $book->getElementsByTagName( "title" );
$title = $titles->item(0)->nodeValue;
echo "$title - $author - $publisher\n";
echo "<br>";
}
?>

<?php
$g_books = array();
$g_elem = null;
function startElement( $parser, $name, $attrs ) 
{
global $g_books, $g_elem;
if ( $name == &#39;BOOK&#39; ) $g_books []= array();
$g_elem = $name;
}
function endElement( $parser, $name ) 
{
global $g_elem;
$g_elem = null;
}
function textData( $parser, $text )
{
global $g_books, $g_elem;
if ( $g_elem == &#39;AUTHOR&#39; ||
$g_elem == &#39;PUBLISHER&#39; ||
$g_elem == &#39;TITLE&#39; )
{
$g_books[ count( $g_books ) - 1 ][ $g_elem ] = $text;
}
}
$parser = xml_parser_create();
xml_set_element_handler( $parser, "startElement", "endElement" );
xml_set_character_data_handler( $parser, "textData" );
$f = fopen( &#39;books.xml&#39;, &#39;r&#39; );
while( $data = fread( $f, 4096 ) )
{
xml_parse( $parser, $data );
}
xml_parser_free( $parser );
foreach( $g_books as $book )
{
echo $book[&#39;TITLE&#39;]." - ".$book[&#39;AUTHOR&#39;]." - ";
echo $book[&#39;PUBLISHER&#39;]."\n";
}
?>

<?php
$xml = "";
$f = fopen( &#39;books.xml&#39;, &#39;r&#39; );
while( $data = fread( $f, 4096 ) ) {
  $xml .= $data; 
}
fclose( $f );
preg_match_all( "/\<book\>(.*?)\<\/book\>/s", $xml, $bookblocks );
foreach( $bookblocks[1] as $block )
{
preg_match_all( "/\<author\>(.*?)\<\/author\>/", $block, $author );
preg_match_all( "/\<title\>(.*?)\<\/title\>/",  $block, $title );
preg_match_all( "/\<publisher\>(.*?)\<\/publisher\>/", $block, $publisher );
echo( $title[1][0]." - ".$author[1][0]." - ".$publisher[1][0]."\n" );
}
?>

<?php
  $data = "<root><line /><content language=\"gb2312\">简单的XML数据</content></root>";
  $parser = xml_parser_create(); //创建解析器
  xml_parse_into_struct($parser, $data, $values, $index); //解析到数组
  xml_parser_free($parser); //释放资源
  //显示数组结构
  echo "\n索引数组\n";
  print_r($index);
  echo "\n数据数组\n";
  print_r($values);
?>

<?php
  //创建XML解析器
  $xml_parser = xml_parser_create();
  //使用大小写折叠来保证能在元素数组中找到这些元素名称
  xml_parser_set_option($xml_parser, XML_OPTION_CASE_FOLDING, true);
  //读取XML文件
  $xmlfile = "bb.xml";
  if (!($fp = fopen($xmlfile, "r")))
  {
    die("无法读取XML文件$xmlfile");
  }
  //解析XML文件
  $has_error = false;      //标志位
  while ($data = fread($fp, 4096))
  {
    //循环地读入XML文档，只到文档的EOF，同时停止解析
    if (!xml_parse($xml_parser, $data, feof($fp)))
    {
      $has_error = true;
      break;
    }
  }
  if($has_error)
  { 
    echo "该XML文档是错误的！<br />";
    //输出错误行，列及其错误信息
    $error_line  = xml_get_current_line_number($xml_parser);
    $error_row  = xml_get_current_column_number($xml_parser);
    $error_string = xml_error_string(xml_get_error_code($xml_parser));
    $message = sprintf("［第%d行，%d列］：%s", 
            $error_line,
            $error_row,
            $error_string);
    echo $message;
  }
  else
  {
    echo "该XML文档是结构良好的。";
  }
  //关闭XML解析器指针，释放资源
  xml_parser_free($xml_parser);
?>