php setcookie时值为null或空字符串(删除cookie)-php手册-php.cn

php setcookie时值为null或空字符串(删除cookie)

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Release： 2016-06-13 09:51:08

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在php中设置cookie与删除cookie都可以使用php setcookie来实现，如果设置就设置有值，如果删除就设置 cookie value为空或null或时间过期都可以删除，下面我们来看一些实例。

长久以来，在php中删除cookie的时候，都是使用
bool setcookie ( string $name [, string $value [, int $expire = 0 [, string $path [, string

$domain [, bool $secure = false [, bool $httponly = false ]]]]]] )

$value 随便写， $expire设置为一个已经过去的时间即可。

官方文档中也是这样写的：

http://www.php.net/manual/en/function.setcookie.php

Example #2 setcookie() delete example
When deleting a cookie you should assure that the expiration date is in the past, to trigger

the removal mechanism in your browser. Examples follow how to delete cookies sent in previous

example:

代码如下	复制代码
// set the expiration date to one hour ago setcookie ("TestCookie", "", time() - 3600); setcookie ("TestCookie", "", time() - 3600, "/~rasmus/", "example.com", 1); ?>

今天遇到一件奇怪的事，在setcookie的时候，传了一个空字符串给$value，结果竟然是此cookie被删除了

…

代码如下

复制代码

$name = "post_url";
$value = "";
setcookie($name, $value, time()+60*60*3, "/" );

delete_cookie

相当不解。

去翻php 5.4.13 的源码：

ext/standard/head.c

代码如下

复制代码

173 PHP_FUNCTION(setcookie)
174 {
175     char *name, *value = NULL, *path = NULL, *domain = NULL;
176     long expires = 0;
177     zend_bool secure = 0, httponly = 0;
178     int name_len, value_len = 0, path_len = 0, domain_len = 0;
179
180     if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|slssbb", &name,
181                               &name_len, &value, &value_len, &expires, &path,
182                               &path_len, &domain, &domain_len, &secure, &httponly) ==

FAILURE) {
183         return;
184     }
185
186     if (php_setcookie(name, name_len, value, value_len, expires, path, path_len, domain,

domain_len, secure, 1, httponly TSRMLS_CC) == SUCCESS) {
187         RETVAL_TRUE;
188     } else {
189         RETVAL_FALSE;
190     }
191 }

76 PHPAPI int php_setcookie(char *name, int name_len, char *value, int value_len, time_t

expires, char *path, int path_len, char *domain, int domain_len, int secure, int url_encode,

int httponly TSRMLS_DC)
77 {
78     char *cookie, *encoded_value = NULL;
79     int len=sizeof("Set-Cookie: ");
80     char *dt;
81     sapi_header_line ctr = {0};
82     int result;
83
84     if (name && strpbrk(name, "=,; trn1314") != NULL) {   /* man isspace for 13

and 14 */
85 zend_error( E_WARNING, "Cookie names cannot contain any of the following '=,;

\t\r\n\013\014'" );
86         return FAILURE;
87     }
88
89     if (!url_encode && value && strpbrk(value, ",; trn1314") != NULL) { /* man

isspace for 13 and 14 */
90 zend_error( E_WARNING, "Cookie values cannot contain any of the following ',;

\t\r\n\013\014'" );
91         return FAILURE;
92     }
93
94     len += name_len;
95     if (value && url_encode) {
96         int encoded_value_len;
97
98         encoded_value = php_url_encode(value, value_len, &encoded_value_len);
99         len += encoded_value_len;
100     } else if ( value ) {
101         encoded_value = estrdup(value);
102         len += value_len;
103     }
104     if (path) {
105         len += path_len;
106     }
107     if (domain) {
108         len += domain_len;
109     }
110
111     cookie = emalloc(len + 100);
112
113     if (value && value_len == 0) {
114         /*
115          * MSIE doesn't delete a cookie when you set it to a null value
116          * so in order to force cookies to be deleted, even on MSIE, we
117          * pick an expiry date in the past
118          */
119         dt = php_format_date("D, d-M-Y H:i:s T", sizeof("D, d-M-Y H:i:s T")-1, 1, 0

TSRMLS_CC);
120         snprintf(cookie, len + 100, "Set-Cookie: %s=deleted; expires=%s", name, dt);
121         efree(dt);
122     } else {
123         snprintf(cookie, len + 100, "Set-Cookie: %s=%s", name, value ? encoded_value :

"");
124         if (expires > 0) {
125             const char *p;
126             strlcat(cookie, "; expires=", len + 100);
127             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);
128             /* check to make sure that the year does not exceed 4 digits in length */
129             p = zend_memrchr(dt, '-', strlen(dt));
130             if (!p || *(p + 5) != ' ') {

参数中的value在C语言中的类型是char * ，还有一个 value_len标明了它的长度。
如果value_len为0的话，就写了下面的cookie:
值为”deleted”, 过期时间为 Thu, 01-Jan-1970 08:00:01 CST 或者说是 Thu, 01-Jan-1970 00:00:01

GMT

看来setcookie($name, “”) 确实可以删除这个cookie了…
同理，在php中，strval(NULL) === “” , 所以 setcookie($name, NULL) 也就相当于 setcookie($name,

“”)，同样可以删除此cookie.

另外，比较好奇的是：