setup_config_display_header example

if ( ! empty( $_REQUEST['language'] ) ) {
    $language = preg_replace( '/[^a-zA-Z0-9_]/', '', $_REQUEST['language'] );
} elseif ( isset( $GLOBALS['wp_local_package'] ) ) {
    $language = $GLOBALS['wp_local_package'];
}

switch ( $step ) {
    case -1:
        if ( wp_can_install_language_pack() && empty( $language ) ) {
            $languages = wp_get_available_translations();
            if ( $languages ) {
                setup_config_display_header( 'language-chooser' );
                echo '<h1 class="screen-reader-text">Select a default language</h1>';
                echo '<form id="setup" method="post" action="?step=0">';
                wp_install_language_form( $languages );
                echo '</form>';
                break;
            }
        }

        // Deliberately fall through if we can't reach the translations API.
    case 0: