A brief analysis of the reasons why the value of php $_cookie is different from the stored value

When using PHP $_COOKIE to obtain the cookie value, sometimes the obtained value may be different from the stored value. At this time, we need to do some debugging and inspection of the code.

The following will introduce some reasons that may cause the cookie value obtained to be different from the stored value.

1. Inconsistent variable names

Since the cookie itself is a request header in the standard HTTP protocol, the variable name used when storing the cookie It needs to be consistent with the variable name used when getting it. If the variable names are inconsistent, the value obtained will be different from the value stored.

For example:

// 存入cookie时
setcookie('test', 'abc', time() + 3600, '/');
 
// 获取cookie时
$test = $_COOKIE['Test'];

In this example, the variable name used when storing cookies is 'test', but 'Test' is used when retrieving, which will result in obtaining The value of is different from the stored value.

2. The cookie action path is inconsistent

Similar to the variable name, the cookie action path also needs to be consistent. If the action path is specified when saving the cookie, but not when retrieving it, the value obtained will be different from the value stored.

For example:

// 存入cookie时
setcookie('test', 'abc', time() + 3600, '/test');
 
// 获取cookie时
$test = $_COOKIE['test'];

In this example, the action path is specified as '/test' when storing the cookie, but it is not specified when obtaining the cookie, resulting in different values.

3. The cookie expiration time is inconsistent

If the expiration time is specified when storing the cookie, but the expiration time has exceeded when the cookie is obtained, then The value obtained is null.

For example:

// 存入cookie时
setcookie('test', 'abc', time() + 3600, '/');
 
// 过了过期时间再获取cookie时
sleep(3605);
$test = $_COOKIE['test'];

In this example, the expiration time of the stored cookie is one hour later, but the expiration time has passed when the cookie is obtained, resulting in the obtained value of null.

4. Cookie cross-domain issue

If the domain name where the cookie is stored is inconsistent with the domain name where the cookie is obtained, the cookie value obtained will also be inconsistent with the domain name used to obtain the cookie. Deposits are different.

For example:

// 存入cookie时
setcookie('test', 'abc', time() + 3600, '/', '.example.com');
 
// 在另一个域名上获取cookie时
$test = $_COOKIE['test'];

In this example, the domain name is '.example.com' is specified when storing the cookie, but if you obtain the cookie on another domain name, you will not get the cookie. to or obtain different values.

Summary:

Ensure that the variable name, action path, expiration time, and domain name are consistent to avoid cross-domain cookie issues. These are the key to obtaining cookie values ​​and storing them. The reason why the entered values ​​are different. When debugging code, be sure to pay attention to these issues to avoid unnecessary errors.

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