Searching

index.php

   menu_execute_active_handler();

     call_user_func_array($router_item['page_callback'],
                          $router_item['page_arguments']);

     search_view($type = 'node'); 

       $results = search_data($keys, $type);

         $results = module_invoke($type, 'search', 'search', $keys);

         node_search($op = 'search', $keys = NULL);

           do_search($keys, 'node', 'INNER JOIN {node} n ON n.nid = i.sid ' .
                     $join1 . ' INNER JOIN {users} u ON n.uid = u.uid',
                     $conditions1 . (empty($where1) ? '' : ' AND ' . $where1),
                     $arguments1, $select2, $join2, $arguments2);

       theme('box', t('Search results'), $results);

         $output = $render_function($template_file, $variables);
         // $template_file used here is one associated with the hook of 
         // the module. The configuration for this purpose is defined by
         // hook_theme such as node_theme();

         $hooks = theme_get_registry();
         $template_file = $hooks[$hook]['template'] . $extension;
         theme_render_template($template_file, $variables);

         $contents = ob_get_contents();

   print theme('page', $return);  // theme used here is in directory themes