libxml_set_external_entity_loader
(PHP 5 >= 5.4.0, PHP 7, PHP 8)
libxml_set_external_entity_loader — Changes the default external entity loader
說明
Changes the default external entity loader.
This can be used to suppress the expansion of arbitrary external entities to avoid XXE attacks,
even when LIBXML_NOENT has been set for the respective operation,
and is usually preferable over calling libxml_disable_entity_loader().
參數
-
resolver_function -
A callable with the following signature:
resolver(string$public_id, string$system_id, array$context): resource|string|null-
public_id - The public ID.
-
system_id - The system ID.
-
context -
An array with the four elements
"directory","intSubName","extSubURI"and"extSubSystem".
nullis returned, the entity reference resolution will fail. -
返回值
成功時返回 true， 或者在失敗時返回 false。
範例
示例 #1 libxml_set_external_entity_loader() example
<?php
$xml = <<<XML
<!DOCTYPE foo PUBLIC "-//FOO/BAR" "http://example.com/foobar">
<foo>bar</foo>
XML;
$dtd = <<<DTD
<!ELEMENT foo (#PCDATA)>
DTD;
libxml_set_external_entity_loader(
function ($public, $system, $context) use($dtd) {
var_dump($public);
var_dump($system);
var_dump($context);
$f = fopen("php://temp", "r+");
fwrite($f, $dtd);
rewind($f);
return $f;
}
);
$dd = new DOMDocument;
$r = $dd->loadXML($xml);
var_dump($dd->validate());
?>
以上例程會輸出：
string(10) "-//FOO/BAR"
string(25) "http://example.com/foobar"
array(4) {
["directory"] => NULL
["intSubName"] => NULL
["extSubURI"] => NULL
["extSubSystem"] => NULL
}
bool(true)