The php setcookie value is null or a null string (delete cookie)

Source: Internet
Author: User
Tags cookie names setcookie

For a long time, when deleting cookies in php
Bool setcookie (string $ name [, string $ value [, int $ expire = 0 [, string $ path [, string

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

$ Value can be written at will, and $ expire can be set to a time that has passed.

This is also written in the official document:

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

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

The removal mechanic in your browser. Examples follow how to delete cookies sent in previous

Example:

The code is as follows: Copy code
<? Php
// Set the expiration date to one hour ago
Setcookie ("TestCookie", "", time ()-3600 );
Setcookie ("TestCookie", "", time ()-3600 ,"/~ Rasmus/"," example.com ", 1 );
?>

Today, I encountered a strange thing. When I set the cookie, I passed an empty string to $ value, and the result was that the cookie was deleted.

...

The code is as follows: Copy code

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

Delete_cookie

Rather puzzled.

Go to php 5.4.13 source code:

Ext/standard/head. c

The code is as follows: Copy code

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 )! = ''){

The value type in the parameter is char * in C, and value_len indicates its length.
If value_len is 0, the following cookie is written:
The value is "deleted" and the expiration time is Thu. 01-Jan-1970 08:00:01 CST or Thu, 01-Jan-1970 00:00:01

GMT

It seems that setcookie ($ name, "") can indeed delete this cookie...
Similarly, in php, strval (NULL) === "", so setcookie ($ name, NULL) is equivalent to setcookie ($ name,

You can also delete this cookie.

In addition, I'm curious about the following:

The code is as follows: Copy code
If (value & value_len = 0 ){
}
Else {
}

Else contains the case where value is null. What is the case?

It seems that setcookie ($ name, "") can indeed delete this cookie...
Similarly, in php, strval (NULL) === "", so setcookie ($ name, NULL) is equivalent to setcookie ($ name,

You can also delete this cookie.

In addition, I'm curious about the following:

The code is as follows: Copy code
If (value & value_len = 0 ){
}
Else {
}

Else contains the case where value is null. What is the case?

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