PHP cookie cannot guarantee solution_PHP tutorial

Cookies exist on the client side and have nothing to do with the server. Pay attention to the case problem in your program. Linux is case-sensitive. There is also the configuration of the PHP tutorial, such as whether the configuration of register_globals = Off is the same on both sides. etc.

The meaning of PHP’s @ and # symbols

function foo($n)
{
$result = 1/$n;
Return $result;
}
echo @foo(0); // A division by 0 error will occur in the function, but the error will not be displayed after adding @.
echo "end"; // output end
# Comment symbol

Same as //, # is a single-line comment character (multi-line comment characters are /* */).

Due to the use of @setcookie, even if an error occurs when writing cookies, it will not be output, making it impossible to detect the problem. Finally, change @setcookie to setcookie, and the program outputs the following error message:

Warning: Cannot modify header information - headers already sent by (output started at

After searching on the Internet, I found that there cannot be any output before setting cookie. Then I checked the code and found that nothing was output before setcookie. After searching, I found the problem. The details are as follows :

I visited the WordPress Chinese forum today. The forum is not very popular, but there are still many masters. Experts who can write plug-ins and templates are mixed with beginners who can't even edit files. That's what the forum is like, haha.

I saw the same error mentioned in several posts, such as this one: "Warning: Cannot modify header information - headers already sent by (output started at c:program fileseasyphp1-8wwwwp-config.php: 1) in c:program fileseasyphp1-8wwwwp-login.php on line 9"

This is a very typical question. When the WordPress program is executed, it will first call configuration files such as wp-config.php, and will also call wp-db.php to establish a database tutorial connection for later use. These files just make some settings and do not output html code. After the settings are completed, the program itself begins to execute. Some programs will use the header command to set an HTTP header. Since the HTTP header must be set before the HTML code is output, otherwise the HTML code has already started to be sent to the client, and the HTTP header has already been sent, and there is no way to go back and reset it. This problem is explained in WordPress CodeX: "How do I solve the Headers already sent warning problem?". The article points out: Make sure that each file - especially the wp-config.php file that is often edited - starts with , and there can be no other characters before and after. Specific to the above example, it is obvious that the prompt message says that the first line of wp-config.php starts HTML output. This may be other characters added before the

Solution

The WordPress Chinese forum does not provide a full-text search function. It can only search titles, so I used Google to search Cannot modify header information site:wordpress.org.cn. It seems that many people have encountered this problem. The WordPress currently used by everyone is mainly the original English version of WordPress and several Chinese versions of WordPress. My Chinese package does not contain the wp-config-sample.php file, so it is of course none of my business; the ASCII code used in the original version of WordPress naturally does not contain BOM, and there will be no such errors; the Chinese version of WordPress produced by xigang is in There is a Chinese forum for WordPress. I downloaded WordPress 2.0.4 and 2.0.3 and checked it. There is no problem. In the Chinese version of WordPress 2.0.4 of Diandianyou, the wp-config-sample.php file is used. It’s GB2312 encoding and DOS line endings, GOD! But that’s fine. If someone uses Notepad to modify this file, the DOS line endings will not cause editing problems, and the GB2312 encoding will not cause BOM problems

Cookie usage
Instructions on deleting cookies begin-----

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

To delete a cookie, you need to ensure that its expiration date is in the past to trigger the browser's deletion mechanism.

The following example shows how to delete the cookie just set:
//Set the expiration time to one hour ago
setcookie("TestCookie", "", time() - 3600);
setcookie("TestCookie", "", time() - 3600, "/~rasmus/", ".utoronto.ca", 1);
?>

-----End of instructions on deleting cookies-----

The way to delete a cookie is to set the validity period of the cookie to before the current time, which is what almost all PHP programmers do.

Later, a friend who was new to PHP told me that he wanted to set the value of a cookie to empty in the program, but the cookie was deleted directly. My first reaction at the time was that I didn’t believe it, so I tested it
After a while:
setcookie("testcookie", '');
print_r($_COOKIE);

The result is that the entire $_COOKIE array is empty, not just $_COOKIE['testcookie']. So I used winsock to capture the packet and observed the returned http header. I found that the http header turned out to be "Set-Cookie: testcookie=deleted; expires=Mon, 18-Jun-2007 02:42:33 GMT", which means "setcookie("testcookie ", '');" indeed deletes the cookie testcookie directly, and there is no explanation at all in the PHP manual about this situation.