Comprehensive solution to PHP application problems_PHP tutorial
Use the == comparison operator with caution, because PHP is untyped, but the underlying C implementation engine is typed. In the end, there is type conversion. For example, the result of 0=="abc" is true, which may not be what we want.
Semantically speaking, where there is a clear type, we must use the relevant function to explicitly convert it: intval . . .
Unify the PHP file inclusion path in one place, so that when including files in various places in the project, do not bring the path, just the file name, which facilitates the transfer of files
There are still other problems with PHP applications One is not to use PHP global variables directly in functions or class methods, but to provide a separate proxy for accessing global variables, which can be an object or just a simple function. If you access global variables in a class, modify To use objects that proxy global variables so that there is a clear dependency between the two objects, do not use global variables directly inside the function or variables outside global. A function should only use the data passed in as function parameters. Try not to use global variables and go global everywhere, and be careful about repeated submissions of forms. This can take the form of a token.
Determine whether the system is single entry or multiple entry
Pay attention to the encoding: file storage encoding, page encoding, database encoding, user's operating system encoding (when the user directly enters content on the address, FF, Opera The content will be encoded according to the encoding urlencode of the operating system, and IE6 is as it is)
Do not expose the path of the file
After submitting the request, the user closes the browser or clicks the stop button of the browser or other network reasons After disconnection, whether PHP should continue processing or stop processing, how does PHP know the above situation: connection-handling(ignore_user_abort,register_shutdown_function,connection_status...)
Time zone issue, if the application is distributed
explode applied to a null value will produce an array containing 1 item: array(""), but the latter is not false. That is: null is a false value, but after explode(',',null) it is a true value, so be careful with conditions like if(explode(',',$var))
$var = null ;isset($var) results in false.
Security issues of PHP application
Verify input, do not trust the data from the user (GET, POST, COOKIE). For a PHP application, these data should be filtered uniformly. For example, encoding html tags prevents XSS and prevents SQL injection.
At the same time, PHP needs to verify the content that needs to be verified once, because various verifications on the client can be easily skipped (pseudo forms, disabling tools such as js and firebug that can modify html at will).
Be aware of the size of the data submitted by the user. For example, if the post data or get data is too large, buffer overflow may occur
Be careful with non-PHP files on the server. If the application can upload or download files, avoid reading the file directly through the file name and the file name is provided by the user. The user may provide some files that he should not see, but the PHP program reads them. At the same time, do not display the file path in the returned HTML. The file saving path should not be visible to the user. The user may guess other files that they should not see based on these paths
If the session is saved in a file , and there are other unknown users on the web server (such as rented web hosts), you should modify the storage location of the session file, or write the session to the database through the PHP session handler, because the session is saved in the temporary directory by default , others can access it, which is dangerous if information such as passwords are saved in the session.
The above are the relevant solutions to PHP application problems.

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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