Collection of errors caused by session in php and solutions_PHP tutorial

Some very strange problems often occur in sessions in PHP. Many of these problems are small details. It may be difficult for PHP beginners to find out what the reasons are. Today we have listed almost all the problems caused or caused by sessions. The problems are collected together and the solutions are given one by one. Students in need can take a look. If there are better friends, they can provide them to me.

1>Error message

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Warning: Cannot send session cookie - headers already sent

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Warning: Cannot send session cookie - headers already sent Warning: Cannot send session cache limiter - headers already sent

Warning: Cannot send session cache limiter - headers already sent

The cause of the problem is that when session_start() is used in the program, actual html content has been output before. Even if a message is echoed or printed, the output generated by the echo or print statement is the actual html content output. The solution to this type of problem is to move session_start() to the first line of the program. 2>Error message

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Warning: open(F:/webphpsessiondatasess_76666aecf239891edc98b5, O_RDWR) failed

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Warning: open(F:/webphpsessiondatasess_76666aecf239891edc98b5, O_RDWR ) failed

Such an error statement appears because the session.save_path item in your php.ini is not set properly. The solution is to change

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session.save_path和session.cookie_path 设置置为 session_save_path = c:temp session.cookie_path = c:temp

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session.save_path and session.cookie_path settings are set to session_save_path = c:temp session.cookie_path = c:temp

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错误提示 Warning: Trying to destroy uninitialized session in

Then create a temp directory in the c: directory

3>

A prompt like this is usually caused by you directly calling 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.

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echo SID;

4>How to get the id value of the current session? The easiest way is:

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echo SID;

5> There is no 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 the same error as question 1? Well, is it because I used session_start() before the header?
I carefully checked your PHP program and found that 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 appear in PHP4.1.2.
6> After using session to log in to the main page, how can I use session to restrict login on other pages? . .
Solution:

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session_start();

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session_start(); if(!session_registered(’login’) ││ login != true) { echo “你没有登陆”; exit; }

if(!session_registered(’login’) ││ login != true) {

echo "You are not logged in";
exit;

}

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session_start(); $ok = ‘love you’; session_register($ok); header(”location : next.php”); ?> next.php session_start(); echo $ok; ?>

7> Use session_register() to register the session variable. However, when using header or JavaScript redirection statement, the variable value registered by the session cannot be accessed in the following page.
Program snippet in question:

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session_start();

$ok = ‘love you’;

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header(”Location: next.php” .”?” . SID);

session_register($ok);

header("location : next.php");
?> next.php

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session_register(’data’;); data=array(1,2,3,4);

session_start();
echo $ok;
?>

Solution: When you use functions such as header function or window.location, the session variables registered on your previous page will be easily lost.

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session_start(); $username = ‘;stangly.wrong’;; session_register(’;username’;); echo $HTTP_SESSION_VARS['username']; echo ‘; ’;; echo _SESSION['username']; ?> 10>

solution.

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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

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session_register('data';); data=array(1,2,3,4);

The method is to register first and then assign the value 9>Can I use HTTP_GET_VARS['**'] to access the 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:

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session_start();<🎜> $username = ‘;stangly.wrong’;;<🎜> session_register(’;username’;);<🎜> echo $HTTP_SESSION_VARS['username'];<🎜> echo ‘; ’;; echo _SESSION['username']; ?> 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 unset the session variable.
And session_destroy() clears the current session environment. This means that after you use the session_destroy() function, it is no longer possible to 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.
Routine:

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if(isset(_COOKIE[session_name()])) { session_start(); session_destroy(); unset(_COOKIE[session_name()]); }

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if(isset(_COOKIE[session_name()] )) {

session_start(); session_destroy();

unset(_COOKIE[session_name()]);

} http://www.bkjia.com/PHPjc/632247.html

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http: //www.bkjia.com/PHPjc/632247.htmlTechArticleSome strange problems often occur in sessions in php. Many of these problems are small details. For php It may be difficult for beginners to discover the reason. Today we have put together almost everything...