libxml_set_streams_context()

The libxml_set_streams_context() function sets the stream context that libxml will use the next time it loads or writes a document over a network protocol such as HTTP, HTTPS, or FTP. It is the hook that lets you attach custom request headers, authentication credentials, timeouts, or a proxy to the implicit network request that functions like DOMDocument::load() and simplexml_load_file() perform behind the scenes.

This page explains the signature, when you actually need it, a complete working example, and the most common gotchas.

Syntax

libxml_set_streams_context(resource $context): void

The context applies globally to libxml for the current request and stays in effect until you set a different one or the script ends.

When would I use it?

Most libxml loads read a local file or an already-fetched string, so you never need this function. You reach for it only when libxml itself opens the network connection — i.e. you pass a http://, https://, or ftp:// URL to a loader. Typical cases:

• The remote server requires an Authorization header (Basic auth, a bearer token).
• You need a custom User-Agent, cookie, or other request header.
• You must set a timeout so a slow host doesn't hang your script.
• The request has to go through an HTTP proxy.

If you fetch the XML yourself (for example with cURL or file_get_contents()) and then parse the resulting string with simplexml_load_string() or DOMDocument::loadXML(), libxml never touches the network and this function does nothing useful.

How to use it

Create the context with stream_context_create(), register it, then load your document:

<?php
// 1. Describe the network request.
$context = stream_context_create([
    'http' => [
        'method'  => 'GET',
        'header'  => "Authorization: Basic " . base64_encode('username:password') . "\r\n"
                   . "User-Agent: w3docs-example\r\n",
        'timeout' => 5, // seconds
    ],
]);

// 2. Tell libxml to use it for the next network load.
libxml_set_streams_context($context);

// 3. Load a remote XML file. libxml opens the connection with the headers above.
$doc = new DOMDocument();
$doc->load('https://example.com/feed.xml');

echo $doc->documentElement->nodeName;
?>

Because libxml swallows protocol-level errors, pair this with libxml_use_internal_errors() so you can inspect failures instead of getting silent warnings:

<?php
libxml_use_internal_errors(true);

$context = stream_context_create([
    'http' => ['timeout' => 5],
]);
libxml_set_streams_context($context);

$doc = new DOMDocument();
if (!$doc->load('https://example.com/feed.xml')) {
    foreach (libxml_get_errors() as $error) {
        echo trim($error->message), "\n";
    }
    libxml_clear_errors();
}
?>

See libxml_get_errors() for how to read the collected errors.

Common gotchas

• It only affects network loads. Calling it before parsing a local file or an in-memory string has no effect.
• Multiple headers must be separated by \r\n. The header option is a single string; join lines with "\r\n" (or pass an array of strings).
• Order matters. Call libxml_set_streams_context() before the load() / simplexml_load_file() call, not after.
• No https:// support? The HTTPS stream wrapper requires the OpenSSL extension to be enabled. Without it, libxml cannot open https:// URLs at all.
• Remote loading must be allowed. Some libxml security settings (and the allow_url_fopen ini directive) can block remote document loading entirely.

Related functions

• libxml_use_internal_errors() — capture parser errors instead of emitting warnings.
• libxml_get_errors() — retrieve those captured errors.
• simplexml_load_file() — a SimpleXML loader that also honors the stream context.
• PHP libxml overview — the broader libxml extension.

Conclusion

libxml_set_streams_context() is the bridge between PHP's stream contexts and libxml's network loaders. Whenever you load XML straight from a URL and need authentication, custom headers, a timeout, or a proxy, build a context with stream_context_create() and register it with this function before the load. For local files or pre-fetched strings, you don't need it at all.

Practice