刚才有同学在群里询问：$_COOKIE 的时间是多长，他指的是“我直接用 $_COOKIE存取的”，也就是说用$_COOKIE这个全局变量保存一个值。那么这个值会存在多长时间，而不是用setcookie来指定。
那么这个值到底是保存多长时间呢？在PHP手册上面查询，没有找到结果，最后发现是在php.ini里指定的。
; Lifetime in seconds of cookie or, if 0, until browser is restarted.
session.cookie_lifetime = 0
; The path for which the cookie is valid.
session.cookie_path = /
; The domain for which the cookie is valid.
session.cookie_domain =
; Whether or not to add the httpOnly flag to the cookie, which makes it inaccessible to browser scripting languages such as JavaScript.
session.cookie_httponly =
session.cookie_lifetime = 0
; The path for which the cookie is valid.
session.cookie_path = /
; The domain for which the cookie is valid.
session.cookie_domain =
; Whether or not to add the httpOnly flag to the cookie, which makes it inaccessible to browser scripting languages such as JavaScript.
session.cookie_httponly =
php.ini里面可以设置session.cookie_lifetime这个值，即默认cookie保存多少秒，如果为0的话那么就和浏览器进程是相同的。
<?php
$coo = 'xxx';
$_COOKIE['xxx'] = $coo;
var_dump($_COOKIE);
?>
$coo = 'xxx';
$_COOKIE['xxx'] = $coo;
var_dump($_COOKIE);
?>
结果为 array(2) { ["ZDEDebuggerPresent"]=> string(14) “php,phtml,php3″ ["xxx"]=> string(3) “xxx” }
而如果我把代码改为如下内容
<?php
var_dump($_COOKIE);
?>
var_dump($_COOKIE);
?>
刷新浏览器，结果为：array(1) { ["ZDEDebuggerPresent"]=> string(14) “php,phtml,php3″ }
$_COOKIE默认的值由php.ini中的session.cookie_lifetime指定。
很好，正找呢
