wp-includes/sitemaps/class-wp-sitemaps-renderer.php:251Checks for the availability of the SimpleXML extension and errors if missing.
private function check_for_simple_xml_availability() { if ( ! class_exists( 'SimpleXMLElement' ) ) { add_filter( 'wp_die_handler', static function () { return '_xml_wp_die_handler'; } ); wp_die( sprintf( /* translators: %s: SimpleXML */ esc_xml( __( 'Could not generate XML sitemap due to missing %s extension' ) ), 'SimpleXML' ), esc_xml( __( 'WordPress › Error' ) ), array( 'response' => 501, // "Not implemented". ) ); } }Introduced in 5.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/sitemaps/class-wp-sitemaps-renderer.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.