title: Handle search in Wordpress from WP_List_Table code
body: <p>I need to add support for searching or filter items using <code>WP_List_Table</code> I read and didn't know how to get this done. I've already added the box trough this code:</p>
  
  <pre><code>function ft_list()
  {
      echo '&lt;/pre&gt;&lt;div class="wrap"&gt;&lt;h2&gt;' . __('Frequent Traveler List') . '&lt;/h2&gt;';
      $ftList = new FT_WP_Table();
      $ftList-&gt;search_box('search', 'search_id');
      echo '&lt;/div&gt;';
  }
  </code></pre>
  
  <p>And this is how my <code>prepare_items()</code> functions looks:</p>
  
  <pre><code>public function prepare_items()
  {
      $searchcol = array(
          'firstname',
          'lastname',
          'foid',
          'no_frequent',
          'create_time'
      );
  
      $columns = $this-&gt;get_columns();
      $hidden = array();
      $sortable = $this-&gt;get_sortable_columns();
      $this-&gt;_column_headers = array(
          $columns,
          $hidden,
          $sortable
      );
  
      // SQL results
      $posts = $this-&gt;get_sql_results();
      empty($posts) AND $posts = array();
  
      # &gt;&gt;&gt;&gt; Pagination
      $per_page = $this-&gt;posts_per_page;
      $current_page = $this-&gt;get_pagenum();
      $total_items = count($posts);
      $this-&gt;set_pagination_args(array(
          'total_items' =&gt; $total_items,
          'per_page' =&gt; $per_page,
          'total_pages' =&gt; ceil($total_items / $per_page)
      ));
      $last_post = $current_page * $per_page;
      $first_post = $last_post - $per_page + 1;
      $last_post &gt; $total_items AND $last_post = $total_items;
  
      // Setup the range of keys/indizes that contain 
      // the posts on the currently displayed page(d).
      // Flip keys with values as the range outputs the range in the values.
      $range = array_flip(range($first_post - 1, $last_post - 1, 1));
  
      // Filter out the posts we're not displaying on the current page.
      $posts_array = array_intersect_key($posts, $range);
      # &lt;&lt;&lt;&lt; Pagination
      // Prepare the data
      $permalink = __('Edit:');
  
      foreach ($posts_array as $key =&gt; $post) {
          $link = get_edit_post_link($post-&gt;id);
          $no_title = __('No title set');
          $title = !$post-&gt;firstname ? "&lt;em&gt;{$no_title}&lt;/em&gt;" : $post-&gt;firstname;
          $posts[$key]-&gt;firstname = "&lt;a title='{$permalink} {$title}' href='{$link}'&gt;{$title}&lt;/a&gt;";
      }
      $this-&gt;items = $posts_array;
  }
  </code></pre>
  
  <p>Where I should add the code to filter items based on search parameter?</p>