wp-includes/IXR/class-IXR-server.php:126$error$messageoptionalfalse function error($error, $message = false) { // Accepts either an error object or an error code and message if ($message && !is_object($error)) { $error = new IXR_Error($error, $message); } $this->output($error->getXml()); }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/IXR/class-IXR-server.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.