php session PHP session FAQs and solutions summary

1.
Error message
Warning: Cannot send session cookie - headers already sent
Warning: Cannot send session cache limiter - headers already sent
Analysis and solution
The reason for this type of problem is that you are in the program Use session_start() At this time, the actual html content has been output before. Maybe you say, I don't have it, I just echo or print a message. Sorry, the output generated by your echo or print statement is the actual html content output. The way to solve this kind of problem is to move your session_start() to the first line of the program.
2.
Error message
Warning: open(F:/689phpsessiondatasess_66a39376b873f4daecf239891edc98b5, O_RDWR) failed
Analysis and solution
Such error statements are usually caused by your php The session.save_path item in .ini is not set properly. Solved. The method is to set session.save_path and session.cookie_path to
session_save_path = c:temp
session.cookie_path = c:temp
Then create a temp directory in the c: directory, you can
3.
Error message
War ning : Trying to destroy uninitialized session in
Analysis and solutions
When prompts like this occur, it is usually caused by you directly adjusting the session_destroy() function. Many friends think that the session_destroy() function can run independently, but this is not the case. The solution is to use session_start() to enable the session function before you call the session_destroy() function.
4. Question: How to get the id value of the current session?
The easiest way is:
echo SID;
You will find out.
5. Question: My program does not have any output before calling the header function. Although I include a config.php file, there is no output in the config.php file. Why does the session still report problems? 1The same error, is it because I used session_start() before header?
Answer: Maybe you have carefully checked your php program, and there is indeed no output before referencing header(). And there is no output in your include file! But do you use the cursor keys to move the check after the end statement of the PHP code?>? Then you will find that after ?>, there is a blank line or a few spaces. If you delete these blank lines or spaces, the problem will be solved.
Note: This problem will occur in PHP4.1.2 and higher versions, and has not been tested.
6. Question: After using session to log in to the main page, how can I use session to restrict login on other pages? . .
Answer: The simplest method is
session_start();
if(!session_registered('login') ││ $login != true) {
echo "You are not logged in";
exit;
}
7. Question: I used session_register() to register the session variable, but when I use header or JavaScript redirection statement, I cannot access the variable value registered by the session on the following page. How to solve it?
The program fragment of the question:
gt;
next.php
  session_start();
echo $ok;
?>
Solution:
When you use a function like header function or window.location, the session registered on your previous page Variables will be easily lost. There is still no detailed answer to the reason for this problem.
But there is a solution. As shown below
header("Location: next.php" ."?" . SID);
When jumping to the next page, use the current id of the session as a parameter and pass it to the next page.
8. How to pass array in session
session_register('data');
$data=array(1,2,3,4);
The method is to register first and then assign the value
9. Question 9: Can I use something like $ What about HTTP_GET_VARS['**'] method to access session value?
Answer: Yes, you can use the following global array to access the session to enhance the security of the web page
$HTTP_SESSION_VARS
$_SESSION
Routine:
session_start();
$username = 'stangly.wr ong' ;
session_register('username');
echo $HTTP_SESSION_VARS['username'];
echo '
';
echo $_SESSION['username'];
?>
php enthusiast site http://www. phpfans.net provides all information for phper.
Please refer to this routine to modify the program to suit your own needs.
Question 10: What is the difference between session_unregister() and session_destroy()?
The main function of the session_unregister() function is to unregister the current session variable. However, it should be noted that if you use $HTTP_SESSION_VARS or $_SESSION to reference the session variable in the current page, then you may need to cooperate with unset() to unregister the session variable.
And session_destroy() clears the current session environment. This means that after you use the session_destroy() function, you can no longer use session_is_registered() to detect session variables. But it should be noted that it cannot clear the session in the global or use the session cookie. So before using session_destroy, it is best not to use $HTTP_SESSION_VARS $_SESSION to access the session. (Translated from php.net)
Example Process:
if(isset($_COOKIE[session_name()])) {
session_start();
session_destroy();
unset($_COOKIE[session_name()]);
}

The above introduces the collection of common problems and solutions to php session PHP session, including the content of php session. I hope it will be helpful to friends who are interested in PHP tutorials.