大多数人都忘记了这只能在本地机器上工作。 在某个域上，您将需要类似此示例的模式。

setcookie("example_cookie", 'password', time()-3600, "/", $_SERVER['SERVER_NAME']);

如果您将cookie设置为过去过期时间，浏览器将删除它。参见setcookie() delete example at php.net

$cookie_name = "my cookie";
$cookie_value = "my value";
$cookie_new_value = "my new value";

// Create a cookie,
setcookie($cookie_name, $cookie_value , time() + (86400 * 30), "/"); //86400 = 24 hours in seconds

// Get value in a cookie,
$cookie_value = $_COOKIE[$cookie_name];

// Update a cookie,
setcookie($cookie_name, $cookie_new_value , time() + (86400 * 30), "/");

// Delete a cookie,
setcookie($cookie_name, '' , time() - 3600, "/"); //  time() - 3600 means, set the cookie expiration date to the past hour.

要删除所有cookie，您可以这样写:

foreach ($_COOKIE as $key => $value) {
    unset($value);
    setcookie($key, '', time() - 3600);
}

请参阅PHP文档中标记为“示例#2 setcookie() delete Example”的示例。要清除浏览器中的cookie，您需要告诉浏览器该cookie已经过期……然后浏览器将删除它。unset只是从cookie数组中移除'hello' cookie。

只要将cookie的值设置为false就可以取消设置:

setcookie('cookiename', false);