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php 删除cookie有效方法

 

php 删除cookie有效方法
关于删除cookie的说明开始-----

bool setcookie ( string name [, string value [, int expire [, string path [, string domain [, bool secure]]]]] )

要删除cookie需要确保它的失效期是在过去,才能触发浏览器的删除机制。

下面的例子说明了如何删除刚才设置的cookie:
//将过期时间设为一小时前
setcookie("TestCookie", "", time() - 3600);
setcookie("TestCookie", "", time() - 3600, "/~rasmus/", ".utoronto.ca", 1);
?>


-----关于删除cookie的说明结束-----

删除一个cookie的方法就是把这个cookie的有效期设置为当前时间以前,这也是几乎所有php程序员都会这么做。

后来一个初接触php的朋友告诉我,他在程序中本想把一个cookie的值设置为空,结果导致这个cookie直接被删除。我当时的第一反应是不相信,于是测试
了一下:
setcookie("testcookie", '');
print_r($_COOKIE);


结果果然是整个$_COOKIE数组都是空的,而非仅仅$_COOKIE['testcookie']为空。于是用winsock抓包,观察返回的http头,发现http头竟然是“Set-Cookie: testcookie=deleted; expires=Mon, 18-Jun-2007 02:42:33 GMT”,这说明“setcookie("testcookie", '');”的的确确是将testcookie这个cookie直接删除,而关于这种情况在php手册中完全没有说明。

最后阅读php源码,终于发现真相(这就是开源的好处了,有什么不清楚的内幕,直接查源码)。

以下代码可以在php5.20的linux源码包中ext/standard/head.c第99行附近找到:
if (value && value_len == 0) {
    /*
     * MSIE doesn't delete a cookie when you set it to a null value
     * so in order to force cookies to be deleted, even on MSIE, we
     * pick an expiry date 1 year and 1 second in the past
     */
    time_t t = time(NULL) - 31536001;
    dt = php_format_date("D, d-M-Y H:i:s T", sizeof("D, d-M-Y H:i:s T")-1, t, 0 TSRMLS_CC);
    sprintf(cookie, "Set-Cookie: %s=deleted; expires=%s", name, dt);
    efree(dt);
} else {
    sprintf(cookie, "Set-Cookie: %s=%s", name, value ? encoded_value : "");
    if (expires > 0) {
        strcat(cookie, "; expires=");
        dt = php_format_date("D, d-M-Y H:i:s T", sizeof("D, d-M-Y H:i:s T")-1, expires, 0 TSRMLS_CC);
        strcat(cookie, dt);
        efree(dt);
    }
}


源码中清清楚楚的显示“if (value && value_len == 0)”,当“value_len”为0时,“sprintf(cookie, "Set-Cookie: %s=deleted; expires=%s", name, dt);”会发送删除cookie的http头给浏览器。

最后我们可以得出结论:在php中使用“setcookie($cookiename, '');”或者“setcookie($cookiename, NULL);”都会删除cookie,当然这些手册中并没有。

来源:http://www.111cn.net/phper/21/f0eace11b1229a0f2c7c54e3c1ea4654.htm

1楼feimengv
开源代码就是爽
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