# libxml_set_external_entity_loader

(PHP 5 >= 5.4.0, PHP 7)

libxml_set_external_entity_loader — Changes the default external entity loader

### 说明

libxml_set_external_entity_loader ( callable `$resolver_function` ) : bool

Changes the default external entity loader.

### 参数

`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`.

### 返回值

成功时返回 `TRUE`， 或者在失败时返回 `FALSE`。

### 范例

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());
    ?>

以上例程会输出：

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

### 参见

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