(PHP 5 >= 5.0.1)
tidyNode::isHtml — Checks if a node is part of a HTML document
Tells if the node is part of HTML document.
   Returns TRUE if the node is part of a HTML document, FALSE otherwise.
  
Example #1 Extract HTML code from a mixed HTML document
<?php
$html = <<< HTML
<html><head>
<?php echo '<title>title</title>'; ?>
<# 
  /* JSTE code */
  alert('Hello World'); 
#>
</head>
<body>
<?php
  // PHP code
  echo 'hello world!';
?>
<%
  /* ASP code */
  response.write("Hello World!")
%>
<!-- Comments -->
Hello World
</body></html>
Outside HTML
HTML;
$tidy = tidy_parse_string($html);
$num = 0;
get_nodes($tidy->html());
function get_nodes($node) {
    // check if the current node is of requested type
    if($node->isHtml()) {
        echo "\n\n# html node #" . ++$GLOBALS['num'] . "\n";
        echo $node->value;
    }
    // check if the current node has childrens
    if($node->hasChildren()) {
        foreach($node->child as $child) {
            get_nodes($child);
        }
    }
}
?>
The above example will output:
# html node #1
<html>
<head>
<?php echo '<title>title</title>'; ?><# 
  /* JSTE code */
  alert('Hello World'); 
#>
<title></title>
</head>
<body>
<?php
  // PHP code
  echo 'hello world!';
?><%
  /* ASP code */
  response.write("Hello World!")
%><!-- Comments -->
Hello WorldOutside HTML
</body>
</html>
# html node #2
<head>
<?php echo '<title>title</title>'; ?><# 
  /* JSTE code */
  alert('Hello World'); 
#>
<title></title>
</head>
# html node #3
<?php echo '<title>title</title>'; ?>
# html node #4
<# 
  /* JSTE code */
  alert('Hello World'); 
#>
# html node #5
<title></title>
# html node #6
<body>
<?php
  // PHP code
  echo 'hello world!';
?><%
  /* ASP code */
  response.write("Hello World!")
%><!-- Comments -->
Hello WorldOutside HTML
</body>
# html node #7
<?php
  // PHP code
  echo 'hello world!';
?>
# html node #8
<%
  /* ASP code */
  response.write("Hello World!")
%>
# html node #9
<!-- Comments -->
# html node #10
Hello World
# html node #11
Outside HTML
Note:
This function was named tidy_node::is_html() in PHP 4/Tidy 1.