我需要重写此URLhttp://example.com/news/?news_id=2 到http://example.com/news/2 其中新闻是页面，2是news_id

I have added following code in functions.php:

function add_news_rewrite_rule() {
    add_rewrite_tag("%news_id%", \'([^/]*)\');
    add_rewrite_rule(\'^news/([^/]*)/?\',\'index.php?pagename=news&news_id=$matches[1]\',\'top\');    
}
add_action( \'init\', \'add_news_rewrite_rule\' );

function my_insert_query_vars( $vars ){
    array_push($vars, \'news_id\');
    return $vars;
}
add_filter( \'query_vars\',\'my_insert_query_vars\' ); 

但这是行不通的。请帮帮我。