此示例用于加亮 XML 代码。举例说明如何使用外部实体引用来包含和解析其他文档，及处理指令是如何被处理的，及判断处理指令所包含代码是否“可信任”的一种方法
用于此示例的 XML 文档位于此示例的下方（xmltest.xml 和 xmltest2.xml）。
示例 #1 外部实体示例
<?php
$file = "xmltest.xml";
function trustedFile($file)
{
// 仅信任本地文件
if (!preg_match("@^([a-z][a-z0-9+.-]*)\:\/\/@i", $file)
&& fileowner($file) == getmyuid()) {
return true;
}
return false;
}
function startElement($parser, $name, $attribs)
{
echo "<<font color=\"#0000cc\">$name</font>";
if (count($attribs)) {
foreach ($attribs as $k => $v) {
echo " <font color=\"#009900\">$k</font>=\"<font
color=\"#990000\">$v</font>\"";
}
}
echo ">";
}
function endElement($parser, $name)
{
echo "</<font color=\"#0000cc\">$name</font>>";
}
function characterData($parser, $data)
{
echo "<b>$data</b>";
}
function PIHandler($parser, $target, $data)
{
switch (strtolower($target)) {
case "php":
global $parser_file;
// 如何要解析的文档是“可信任”的, 则说明可安全
// 地执行其内部的 PHP 代码。否则，显示代码内容。
if (trustedFile($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);
?>
示例 #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>
此文件包含在 xmltest.xml 中：
示例 #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>