title: I cant drop tables after uninstalling plugin in WP, why?
body: <p>In <code>uninstall.php</code> I have this part of code, when I delete my plugin after it, I see that in my db I have all my plugin tables:</p>
  
  <pre><code>&lt;?php
  function my_plugin_remove_database()
  {
      global $wpdb;
      $quiz_categories_table      =   $wpdb-&gt;prefix . 'aysquiz_quizcategories';
      $quizes_table               =   $wpdb-&gt;prefix . 'aysquiz_quizes';
      $questions_table            =   $wpdb-&gt;prefix . 'aysquiz_questions';
      $question_categories_table  =   $wpdb-&gt;prefix . 'aysquiz_categories';
      $answers_table              =   $wpdb-&gt;prefix . 'aysquiz_answers';
      $reports_table              =   $wpdb-&gt;prefix . 'aysquiz_reports';
      $themes_table               =   $wpdb-&gt;prefix . 'aysquiz_themes';
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$quiz_categories_table."`");
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$quizes_table."`");
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$questions_table."`");
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$question_categories_table."`");
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$answers_table."`");
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$reports_table."`");
      $wpdb-&gt;query("DROP TABLE IF EXISTS `".$themes_table."`");
  }
  
  register_uninstall_hook( __FILE__, 'my_plugin_remove_database' );
  </code></pre>