


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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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
代码如下 | 复制代码 |
Warning: open(F:/webphpsessiondatasess_76666aecf239891edc98b5, O_RDWR) failed |
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Warning: open(F:/webphpsessiondatasess_76666aecf239891edc98b5, O_RDWR ) failed
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代码如下 | 复制代码 |
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 |
代码如下 | 复制代码 |
错误提示 Warning: Trying to destroy uninitialized session in |
3>
代码如下 | 复制代码 |
echo SID; |
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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();
echo "You are not logged in";
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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’;
header("location : next.php");
session_start(); |
Solution: When you use functions such as header function or window.location, the session variables registered on your previous page will be easily lost.
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']; ?> 10> |
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header("Location: next.php" . "?" .SID); |
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session_register('data';); data=array(1,2,3,4); |
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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()] )) { |
unset(_COOKIE[session_name()]);
www.bkjia.comtruehttp: //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...
What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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