Cet exemple remplace les balises XML d'un document par des balises HTML. Les éléments inconnus seront ignorés. Bien entendu, cet exemple sera applique à un type précis de fichiers XML.

$file = "data.xml";
$map_array = array(
    "BOLD"     => "B",
    "EMPHASIS" => "I",
    "LITERAL"  => "TT"
);

function elementDebut($parser, $name, $attrs)
{
    global $map_array;
    if ($htmltag = $map_array[$name]) {
        print "<$htmltag>";
    }
}

function elementFin($parser, $name)
{
    global $map_array;
    if ($htmltag = $map_array[$name]) {
        print "</$htmltag>";
    }
}

function characterData($parser, $data)
{
    print $data;
}

$xml_parser = xml_parser_create();
// use case-folding so we are sure to find the tag in $map_array
xml_parser_set_option($xml_parser, XML_OPTION_CASE_FOLDING, true);
xml_set_element_handler($xml_parser, "elementDebut", "elementFin");
xml_set_character_data_handler($xml_parser, "characterData");
if (!($fp = fopen($file, "r"))) {
    die("could not open XML input");
}
while ($data = fread($fp, 4096)) {
    if (!xml_parse($xml_parser, $data, feof($fp))) {
        die(sprintf("erreur XML: %s à la ligne %d",
                    xml_erreur_string(xml_get_erreur_code($xml_parser)),
                    xml_get_current_line_number($xml_parser)));
    }
}
xml_parser_free($xml_parser);

$file = "xmltest.xml";

function trustedFile($file)
{
    // only trust local files owned by ourselves
    if (!eregi("^([a-z]+)://", $file) && fileowner($file) == getmyuid()) {
        return true;
    }
    return false;
}

function elementDebut($parser, $name, $attribs)
{
    print "&lt;<font color=\"#0000cc\">$name</font>";
    if (sizeof($attribs)) {
        while (list($k, $v) = each($attribs)) {
            print " <font color=\"#009900\">$k</font>=\"<font color=\"#990000\">$v</font>\"";
        }
    }
    print "&gt;";
}

function elementFin($parser, $name)
{
    print "&lt;/<font color=\"#0000cc\">$name</font>&gt;";
}

function characterData($parser, $data)
{
    print "<b>$data</b>";
}

function PIHandler($parser, $target, $data)
{
    switch (strtolower($target)) {
        case "php":
            global $parser_file;
            // Si le document analysé est "fiable", on peut penser qu'il 
            // est bon pour être exécuté comme code PHP.  Si non, on
            // affiche simplement le code.
            if (trustedFile($parser_file[$parser])) {
                eval($data);
            } else {
                printf("code PHP non fiable: <i>%s</i>", htmlspecialchars($data));
            }
            break;
    }
}

function defaultHandler($parser, $data)
{
    if (substr($data, 0, 1) == "&" && substr($data, -1, 1) == ";") {
        printf('<font color="#aa00aa">%s</font>', htmlspecialchars($data));
    } else {
        printf('<font size="-1">%s</font>', htmlspecialchars($data));
    }
}

function externalEntityRefHandler($parser, $openEntityNames, $base, $systemId,
                                  $publicId)
{
    if ($systemId) {
        if (!list($parser, $fp) = new_xml_parser($systemId)) {
            printf("Impossible d'accéder à l'entité %s à la ligne %s\n", $openEntityNames,
                   $systemId);
            return false;
        }
        while ($data = fread($fp, 4096)) {
            if (!xml_parse($parser, $data, feof($fp))) {
                printf("XML erreur: %s à la ligne %d lors de l'analyse de l'entité %s\n",
                       xml_erreur_string(xml_get_erreur_code($parser)),
                       xml_get_current_line_number($parser), $openEntityNames);
                xml_parser_free($parser);
                return false;
            }
        }
        xml_parser_free($parser);
        return true;
    }
    return false;
}


function new_xml_parser($file) {
    global $parser_file;

    $xml_parser = xml_parser_create();
    xml_parser_set_option($xml_parser, XML_OPTION_CASE_FOLDING, 1);
    xml_set_element_handler($xml_parser, "elementDebut", "elementFin");
    xml_set_character_data_handler($xml_parser, "characterData");
    xml_set_processing_instruction_handler($xml_parser, "PIHandler");
    xml_set_default_handler($xml_parser, "defaultHandler");
    xml_set_external_entity_ref_handler($xml_parser, "externalEntityRefHandler");
    
    if (!($fp = @fopen($file, "r"))) {
        return false;
    }
    if (!is_array($parser_file)) {
        settype($parser_file, "array");
    }
    $parser_file[$xml_parser] = $file;
    return array($xml_parser, $fp);
}

if (!(list($xml_parser, $fp) = new_xml_parser($file))) {
    die("could not open XML input");
}

print "<pre>";
while ($data = fread($fp, 4096)) {
    if (!xml_parse($xml_parser, $data, feof($fp))) {
        die(sprintf("XML erreur: %s à la ligne %d\n",
                    xml_erreur_string(xml_get_erreur_code($xml_parser)),
                    xml_get_current_line_number($xml_parser)));
    }
}
print "</pre>";
print "parse complete\n";
xml_parser_free($xml_parser);

?>

<?xml version='1.0'?>
<!DOCTYPE chapter SYSTEM "/just/a/test.dtd" [
<!ENTITY plainEntity "FOO entity">
<!ENTITY systemEntity SYSTEM "xmltest2.xml">
]>
<chapter>
 <TITLE>Title &plainEntity;</TITLE>
 <para>
  <informaltable>
   <tgroup cols="3">
    <tbody>
     <row><entry>a1</entry><entry morerows="1">b1</entry><entry>c1</entry></row>
     <row><entry>a2</entry><entry>c2</entry></row>
     <row><entry>a3</entry><entry>b3</entry><entry>c3</entry></row>
    </tbody>
   </tgroup>
  </informaltable>
 </para>
 &systemEntity;
 <sect1 id="about">
  <title>About this Document</title>
  <para>
   <!-- this is a comment -->
   <?php print 'Hi!  This is PHP version '.phpversion(); ?>
  </para>
 </sect1>
</chapter>

<?xml version="1.0"?>
<!DOCTYPE foo [
<!ENTITY testEnt "test entity">
]>
<foo>
 <element attrib="value"/>
 &testEnt;
 <?php print "This is some more PHP code being executed."; ?>
</foo>