WordPress实现发布时间超过15天的文章中展示广告的方法

function is_old_post($post_id=null){ 
$days = 15; 
global $wp_query; 
if(is_single() || is_page()) { 
if(!$post_id) { 
$post_id = $wp_query->post->ID; 
} 
$current_date = time(); 
$offset = $days *60*60*24; 
$post_id = get_post($post_id); 
$post_date = mysql2date('U',$post_id->post_date); 
$cunning_math = $post_date + $offset; 
$test = $current_date - $cunning_math; 
if($test > 0){ 
$return = true; 
}else{ 
$return = false; 
} 
}else{ 
$return = false; 
} 
return $return; 
}

< ?php if(is_old_post()){ ?> 
INSERT AD CODE HERE 
< ?php } ?>