I want to use my personal plugin only in some pages.
If I remove the add_action function (‘the_content’, ‘my_plugin_content’); the plugin does not show me the content of the other pages that are not in in_array ();

function my_plugin_content($content){
  global $post; global $wp; global $wpdb;
  $page =array('page1', 'page2','page3');
  $current_page = $wp->request;
  if(in_array($current_page, $page))
  {
   $old_content=$post->post_content;
   $sql = "UPDATE wp_posts SET post_content = '' WHERE ID = $post->ID";
   $wpdb->get_results($sql);
   include_once(plugin_dir_path( __FILE__ ).'loaders/loaders.php');
   $obj = new Loader;
   $content.=$obj->controller($current_page);
   $my_post = array(); 
   $my_post['ID'] = $post->ID;
   $my_post['post_content']=$content;
   wp_update_post($my_post);
 }
}
add_action('the_content', 'my_plugin_content');