# libxml_set_external_entity_loader

(PHP 5 >= 5.4.0, PHP 7)

libxml_set_external_entity_loader — Changes the default external entity loader

### Description

libxml_set_external_entity_loader ( callable `$resolver_function` ) : bool

Changes the default external entity loader.

### Parameters

`resolver_function`

  A callable that takes three arguments. Two strings, a public id and system id, and a context (an array with four keys) as the third argument. This callback should return a resource, a string from which a resource can be opened, or `NULL`.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Examples

Example #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());
?>`

The above example will output:

    string(10) "-//FOO/BAR"
    string(25) "http://example.com/foobar"
    array(4) {
        ["directory"]    => NULL
        ["intSubName"]   => NULL
        ["extSubURI"]    => NULL
        ["extSubSystem"] => NULL
    }
    bool(true)

### See Also

- libxml_disable_entity_loader() - Disable the ability to load external entities