


Summary of 14 problems that give PHP beginners a headache_PHP Tutorial
1. Variables cannot be passed between pages
The automatic global variables of get, post, and session are turned off in the latest PHP version, so to get the submitted variables from the previous page, use $_GET['foo'], $_POST['foo'], $_SESSION['foo'] to get. Of course, you can also modify the automatic global variables to be on (php.ini is changed to register_globals = On); considering compatibility, it is better to force yourself to become familiar with the new writing method.
2. Using the get method to pass Chinese parameters to apache2 under Win32 will cause an error
test.php?a=Hello&b=Hello
Passing parameters will cause an internal error
Solution: "test.php?a=".urlencode(Hello)."&b=".urlencode(Hello)
......
3. Session under win32 does not work properly
php.ini default session.save_path = /tmp
This is obviously a configuration under Linux. PHP cannot read and write session files under win32, causing the session to be unusable
Just change it to an absolute path, for example session.save_path = c:windowstemp
4. Display error message
When display_errors = On and error_reporting = E_ALL in php.ini, all errors and prompts will be displayed. It is best to turn it on during debugging for error correction. If you use the previous PHP writing method, most of the error messages are about undefined variables. . There will be a prompt when a variable is called before it is assigned a value. The solution is to detect or shield it.
For example, to display $foo, you can if(isset($foo)) echo $foo or echo @$foo
5. Mail() cannot send emails under Win32
Sendmail configured under Linux can be sent. Under win32, you need to call the smtp server to send emails. Modify the SMTP = ip in php.ini //ip is an smtp server without verification function (hard to find on the Internet) , the best solution for sending emails in php is to use socket to send directly to the other party's email server without forwarding the server.
6. If there is no password set for the initial installation of mysql, you should use
update mysql.user set password="yourpassword" where user="root"
Change password
7. header already sent
This error usually occurs when you use HEADER. It may be due to several reasons: 1. You PRING or ECHO before using HEADER 2. There is a blank line in front of your current file 3. You may have INCLUDEd a file , this error will also occur if there is a blank line at the end of the file or the output.
8. There is no change after changing php.ini
Restart the web server, such as IIS, Apache, etc., and then the latest settings will be applied
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PHP is a server-side scripting language used for dynamic web development and server-side applications. 1.PHP is an interpreted language that does not require compilation and is suitable for rapid development. 2. PHP code is embedded in HTML, making it easy to develop web pages. 3. PHP processes server-side logic, generates HTML output, and supports user interaction and data processing. 4. PHP can interact with the database, process form submission, and execute server-side tasks.

PHP has shaped the network over the past few decades and will continue to play an important role in web development. 1) PHP originated in 1994 and has become the first choice for developers due to its ease of use and seamless integration with MySQL. 2) Its core functions include generating dynamic content and integrating with the database, allowing the website to be updated in real time and displayed in personalized manner. 3) The wide application and ecosystem of PHP have driven its long-term impact, but it also faces version updates and security challenges. 4) Performance improvements in recent years, such as the release of PHP7, enable it to compete with modern languages. 5) In the future, PHP needs to deal with new challenges such as containerization and microservices, but its flexibility and active community make it adaptable.

The core benefits of PHP include ease of learning, strong web development support, rich libraries and frameworks, high performance and scalability, cross-platform compatibility, and cost-effectiveness. 1) Easy to learn and use, suitable for beginners; 2) Good integration with web servers and supports multiple databases; 3) Have powerful frameworks such as Laravel; 4) High performance can be achieved through optimization; 5) Support multiple operating systems; 6) Open source to reduce development costs.

PHP is not dead. 1) The PHP community actively solves performance and security issues, and PHP7.x improves performance. 2) PHP is suitable for modern web development and is widely used in large websites. 3) PHP is easy to learn and the server performs well, but the type system is not as strict as static languages. 4) PHP is still important in the fields of content management and e-commerce, and the ecosystem continues to evolve. 5) Optimize performance through OPcache and APC, and use OOP and design patterns to improve code quality.

PHP and Python have their own advantages and disadvantages, and the choice depends on the project requirements. 1) PHP is suitable for web development, easy to learn, rich community resources, but the syntax is not modern enough, and performance and security need to be paid attention to. 2) Python is suitable for data science and machine learning, with concise syntax and easy to learn, but there are bottlenecks in execution speed and memory management.

PHP is used to build dynamic websites, and its core functions include: 1. Generate dynamic content and generate web pages in real time by connecting with the database; 2. Process user interaction and form submissions, verify inputs and respond to operations; 3. Manage sessions and user authentication to provide a personalized experience; 4. Optimize performance and follow best practices to improve website efficiency and security.

PHP uses MySQLi and PDO extensions to interact in database operations and server-side logic processing, and processes server-side logic through functions such as session management. 1) Use MySQLi or PDO to connect to the database and execute SQL queries. 2) Handle HTTP requests and user status through session management and other functions. 3) Use transactions to ensure the atomicity of database operations. 4) Prevent SQL injection, use exception handling and closing connections for debugging. 5) Optimize performance through indexing and cache, write highly readable code and perform error handling.

Using preprocessing statements and PDO in PHP can effectively prevent SQL injection attacks. 1) Use PDO to connect to the database and set the error mode. 2) Create preprocessing statements through the prepare method and pass data using placeholders and execute methods. 3) Process query results and ensure the security and performance of the code.


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