Analysis of common session problems in php_PHP tutorial

PHP’s session function has always been difficult for many beginners. Even some veterans are confused sometimes. This article makes a simple summary of these issues for everyone’s reference.

1. Error message

Quote

The code is as follows

Copy code

代码如下	复制代码
Warning: Cannot send session cookie - headers already sent Warning: Cannot send session cache limiter - headers already sent

Warning: Cannot send session cookie - headers already sent

Warning: Cannot send session cache limiter - headers already sent

Analysis and solutions

The reason for this type of problem is that when you use session_start() in the program, 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

代码如下	复制代码
Warning: open(F:/689phpsessiondatasess_66a39376b873f4daecf239891edc98b5, O_RDWR) failed

Quote

The code is as follows	Copy code
Warning: open(F:/689phpsessiondatasess_66a39376b873f4daecf239891edc98b5, O_RDWR) failed

Analysis and solutions
Such an error statement usually occurs because the session.save_path item in your php.ini is not set properly. The solution is to set the session.save_path and session.cookie_path settings to

代码如下	复制代码
session_save_path = c:temp session.cookie_path = c:temp

Quote

The code is as follows	Copy code
session_save_path = c:temp session.cookie_path = c:temp

Then create a temp directory in the c: directory

代码如下	复制代码
Warning: Trying to destroy uninitialized session in

3. Error message Quote

The code is as follows	Copy code
Warning: Trying to destroy uninitialized session in

Analysis and solutions
This kind of prompt 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.

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 The same error as question 1, is it because I used session_start() before the 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 this 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 to use session to restrict login on other pages
Answer: The easiest way is

The code is as follows

Copy code

session_start();

代码如下	复制代码
session_start();   if(!session_registered('login') ││ $login != true) {   echo "你没有登陆";   exit;   }   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;

}

session_start();
if(!session_registered('login') ││ $login != true) {

echo "You are not logged in";

exit;

}

代码如下	复制代码
session_start();   $ok = 'love you';   session_register('ok');   header("location : next.php");   ? >   session_start(); $ok = 'love you'; session_register('ok'); header("location : next.php"); ? >

7. Question: I use session_register() to register the session variable, but when I use header or redirection statement of javs script, I cannot access the variable value registered by the session in the following page. How to solve it?

代码如下	复制代码
session_start();   echo $ok;   ? >   session_start(); echo $ok; ? >

Program snippet in question:

The code is as follows

Copy code

session_start(); $ok = 'love you';

代码如下	复制代码
header("Location: next.php" ."?" . SID);   header("Location: next.php" ."?" . SID);

session_register('ok'); header("location : next.php"); ? > session_start(); $ok = 'love you'; session_register('ok'); header("location : next.php"); ?>

next.php

The code is as follows	Copy code
session_start(); echo $ok; ? > session_start(); echo $ok; ?>

Solution: When you use functions such as header function or window.location, the session variable registered on your previous page will be easily lost. There is still no detailed answer to the reason for this problem. But there are solutions. As shown below

The code is as follows	Copy code
header("Location: next.php" ."?" . SID); 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

The code is as follows

代码如下	复制代码
session_register('data');   $data=array(1,2,3,4);   session_register('data'); $data=array(1,2,3,4);

Copy code

session_register('data');

$data=array(1,2,3,4);

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

代码如下	复制代码
session_start();   $username = 'stangly.wrong';   session_register('username');     echo $HTTP_SESSION_VARS['username'];   echo ' ';   echo $_SESSION['username'];   ? >   session_start(); $username = 'stangly.wrong'; session_register('username'); echo $HTTP_SESSION_VARS['username']; echo ' '; echo $_SESSION['username']; ? >

The method is to register first and then assign the value

9. Question: Can I access the session value using a method like $HTTP_GET_VARS['**']?

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:

代码如下	复制代码
if(isset($_COOKIE[session_name()])) {   session_start();   session_destroy();   unset($_COOKIE[session_name()]);   }

The code is as follows

Copy code

session_start();

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

echo '
'; echo $_SESSION['username']; ?>

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 unset 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. Routine:

The code is as follows

Copy code

if(isset($_COOKIE[session_name() ])) { session_start(); session_destroy(); unset($_COOKIE[session_name()]); }  http://www.bkjia.com/PHPjc/632221.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632221.htmlTechArticlePHP’s session function has always been difficult for many beginners. Even some veterans are confused sometimes. This article makes a simple summary of these issues for everyone to refer to...