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Exemplo de entidade externa do XML

Este exemplo destaca o código XML. Ele ilusta como utilizar um analisador de referência a uma entity externa para incluir e analisar outros documentos, tão bem como PIs (instruções de processo) podem ser processadas, e uma forma de determinar "trust" para PIs contendo códigos.

Documentos XML que podem ser utilizados para este exemplo são encontrados abaixo do exemplo (xmltest.xml e xmltest2.xml.)

Exemplo #1 Exemplo da Entidade Externa

<?php
$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
startElement($parser, $name, $attribs)
{
echo
"&lt;<font color=\"#0000cc\">$name</font>";
if (
count($attribs)) {
foreach (
$attribs as $k => $v) {
echo
" <font color=\"#009900\">$k</font>=\"<font
color=\"#990000\">
$v</font>\"";
}
}
echo
"&gt;";
}

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

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

function
PIHandler($parser, $target, $data)
{
switch (
strtolower($target)) {
case
"php":
global
$parser_file;
// If the parsed document is "trusted", we say it is safe
// to execute PHP code inside it. If not, display the code
// instead.
if (trustedFile($parser_file[$parser])) {
eval(
$data);
} else {
printf("Untrusted PHP code: <i>%s</i>",
htmlspecialchars($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("Could not open entity %s at %s\n", $openEntityNames,
$systemId);
return
false;
}
while (
$data = fread($fp, 4096)) {
if (!
xml_parse($parser, $data, feof($fp))) {
printf("XML error: %s at line %d while parsing entity %s\n",
xml_error_string(xml_get_error_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($xml_parser, "startElement", "endElement");
xml_set_character_data_handler($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");
}

echo
"<pre>";
while (
$data = fread($fp, 4096)) {
if (!
xml_parse($xml_parser, $data, feof($fp))) {
die(
sprintf("XML error: %s at line %d\n",
xml_error_string(xml_get_error_code($xml_parser)),
xml_get_current_line_number($xml_parser)));
}
}
echo
"</pre>";
echo
"parse complete\n";
xml_parser_free($xml_parser);

?>

Exemplo #2 xmltest.xml

<?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;
 <section id="about">
  <title>About this Document</title>
  <para>
   <!-- this is a comment -->
   <?php echo 'Hi!  This is PHP version ' . phpversion(); ?>
  </para>
 </section>
</chapter>

Este arquivo é incluido por xmltest.xml:

Exemplo #3 xmltest2.xml

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

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