PHP有關問題（急）

PHP問題（急）
請各位高手幫忙：下面的緩衝代碼：怎麼樣實現每隔15分鐘就調用一次鑽石榜，魅力榜，職分榜：
//調用緩衝
$cacheM = new Seed_Model_Cache2File();
$money_list = $cacheM->get("money_list");
$extcredits2_list = $cacheM->get("extcredits2_list");
$extcredits1_list = $cacheM->get("extcredits1_list");

if (!isset($money_list)){
//鑽石榜
$userM = new User_Model_User('user');
$money_list = $userM->fetch_rows(array(0,7), $where_str, array('money desc'));
//echo 111;//測試是否在用緩衝；
$cacheM->save("money_list",$money_list);
}
if (!isset($extcredits2_list)){
//魅力榜
$bbsM = new User_Model_Bbs('bbs');
$extcredits2_list = $bbsM->fetch_rows(array(0,7),$where_str,"extcredits2 DESC");
$cacheM->save("extcredits2_list",$extcredits2_list);
}
if (!isset($extcredits1_list)){
//職分榜
$extcredits1_list = $bbsM->fetch_rows(array(0,7),$where_str,"extcredits1 DESC");
$cacheM->save("extcredits1_list",$extcredits1_list);
}

$this->view->money_list = $money_list;
$this->view->extcredits2_list = $extcredits2_list;
$this->view->extcredits1_list = $extcredits1_list;

------解決方案--------------------
使用系統的任務計劃。要不就寫個死迴圈；sleep（15*60）shell調用。

