Explore the underlying operating mechanism of PHP_PHP tutorial
简介
我们从未手动开启过PHP的相关进程,它是随着Apache的启动而运行的;PHP通过mod_php5.so模块和Apache相连(具体说来是SAPI,即服务器应用程序编程接口);
PHP总共有三个模块:内核、Zend引擎、以及扩展层; PHP内核用来处理请求、文件流、错误处理等相关操作; Zend引擎(ZE)用以将源文件转换成机器语言,然后在虚拟机上运行它; 扩展层是一组函数、类库和流,PHP使用它们来执行一些特定的操作。比如,我们需要mysql扩展来连接MySQL数据库; 当ZE执行程序时可能会需要连接若干扩展,这时ZE将控制权交给扩展,等处理完特定任务后再返还;
最后,ZE将程序运行结果返回给PHP内核,它再将结果传送给SAPI层,最终输出到浏览器上。
深入探讨
真是的内部运行过程没有这么简单。以上过程只是个简略版,让我们再深入挖掘一下,看看幕后还发生了些什么。
◆Apache启动后,PHP解释程序也随之启动;
◆PHP的启动过程有两步:
第一步是初始化一些环境变量,这将在整个SAPI生命周期中发生作用;
第二步是生成只针对当前请求的一些变量设置。
PHP启动第一步
不清楚什么第一第二步是什么?别担心,我们接下来详细讨论一下。让我们先看看第一步,也是最主要的一步。要记住的是,第一步的操作在任何请求到达之前就发生了。
启动Apache后,PHP解释程序也随之启动;
PHP调用各个扩展的MINIT方法,从而使这些扩展切换到可用状态。看看php.ini文件里打开了哪些扩展吧; MINIT的意思是“模块初始化”。各个模块都定义了一组函数、类库等用以处理其他请求。
一个典型的MINIT方法如下:
PHP_MINIT_FUNCTION(extension_name){/* Initialize functions, classes etc */} |
PHP启动第二步
当一个页面请求发生时,SAPI层将控制权交给PHP层。于是PHP设置了用于回复本次请求所需的环境变量。同时,它还建立一个变量表,用来存放执行过程中产生的变量名和值。
PHP调用各个模块的RINIT方法,即“请求初始化”。一个经典的例子是Session模块的RINIT,如果在php.ini中启用了Session模块,那在调用该模块的RINIT时就会初始化$_SESSION变量,并将相关内容读入;
RINIT方法可以看作是一个准备过程,在程序执行之间就会自动启动。
一个典型的RINIT方法如下:
PHP_RINIT_FUNCTION(extension_name) {/* Initialize session variables,<br>pre-populate variables, <br>redefine global variables etc */} |
PHP关闭第一步
如同PHP启动一样,PHP的关闭也分两步:
一旦页面执行完毕(无论是执行到了文件末尾还是用exit或die函数中止),PHP就会启动清理程序。它会按顺序调用各个模块的RSHUTDOWN方法。
RSHUTDOWN用以清除程序运行时产生的符号表,也就是对每个变量调用unset函数。
一个典型的RSHUTDOWN方法如下:
PHP_RSHUTDOWN_FUNCTION(extension_name) {/* Do memory management, <br>unset all variables used in the last PHP call etc */} |
PHP关闭第二步
最后,所有的请求都已处理完毕,SAPI也准备关闭了,PHP开始执行第二步:
PHP调用每个扩展的MSHUTDOWN方法,这是各个模块最后一次释放内存的机会。
一个典型的RSHUTDOWN方法如下:
PHP_MSHUTDOWN_FUNCTION(extension_name) {/* Free handlers and persistent memory etc */} |
In this way, the entire PHP life cycle is over. It should be noted that "starting the first step" and "closing the second step" will only be executed when there is no request from the server.

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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