Callback for `wp_kses_normalize_entities()` regular expression.

This function only accepts valid named entity references, which are finite,
case-sensitive, and highly scrutinized by XML validators. HTML named entity
references are converted to their code points.

function wp_kses_xml_named_entities( $matches ) {
	global $allowedentitynames, $allowedxmlentitynames;

	if ( empty( $matches[1] ) ) {
		return '';
	}

	$i = $matches[1];

	if ( in_array( $i, $allowedxmlentitynames, true ) ) {
		return "&$i;";
	} elseif ( in_array( $i, $allowedentitynames, true ) ) {
		return html_entity_decode( "&$i;", ENT_HTML5 );
	}

	return "&$i;";
}