In-depth understanding of PHP kernel (2) Overview - PHP life cycle and Zend engine, -phpzend_PHP tutorial

In-depth understanding of the PHP kernel (2) Overview - PHP life cycle and Zend engine, -phpzend

This article refers to "In-depth understanding of the PHP kernel", address: https://github .com/reeze/tipi

1. SAPI interface

SAPI (Server Application Programming Interface) refers to the programming interface for specific PHP applications. PHP scripts can be executed in many ways: through a web server, the command line, or embedded in other programs.

Although executing scripts through a web server and a command line program looks very different, the actual process is the same. It's just that the web server method returns the php script execution results to the web server, and the command line prints the results to the console.

Script execution starts with the SAPI interface implementation, but different SAPI interface implementations will complete their specific work. For example, Apache’s mod_php SAPI implementation needs to initialize some information obtained from Apache. In the output content, the content Returned to Apache, other SAPI implementations are similar

2. Beginning and ending

(1) PHP will go through two stages after it starts executing: the starting stage before processing the request and the ending stage after the request. There are two processes in the beginning phase: the first process is the module initialization phase (MINIT). During the entire SAPI life cycle (such as the entire life cycle after Apache starts or the entire execution process of the command line program), this process only Do it once . The second process is the module activation phase (RINIT), which occurs in the request phase . For example, if a page is requested through a URL, module activation (RINIT request starts) will be performed before each request. For example, if PHP registers some extension modules, it will call back the MINIT function of all modules in the MINIT stage. The module performs some initialization work at this stage, such as registering constants, defining classes used by the module, etc. The module can implement these callback functions through the following macros during implementation:

<span>PHP_MINIT_FUNCTION(myphpextension)
{
    </span><span>//</span><span> 注册常量或者类等初始化操作</span>
    <span>return</span><span> SUCCESS;      
}</span>

The basic environment of the PHP initialization script after the request arrives, such as creating an execution environment, including a symbol table that saves the variable names and value contents during PHP running, as well as a symbol table of all current functions, classes and other information. Then PHP will call the RINIT function of all modules. At this stage, each module can also perform some related operations. The module RINIR function is similar to the MINIT callback function:

<span>PHP_RINIT_FUNCTION(myphpextension)
{
    </span><span>//</span><span> 例如记录请求开始时间
    </span><span>//</span><span> 随后在请求结束的时候记录结束时间，这样我们就能记录下处理请求所花费的时间了</span>
    <span>return</span><span> SUCCESS;
}</span>

After the request is processed, it enters the end phase. Generally, PHP will enter the end phase when the script is executed to the end or by calling the die() or exit() function. The end phase also has two links: one is to deactivate the module after the request is completed (RSHUTDOWN, corresponding to RINIT), and the other is to close the module when the SAPI life cycle ends (the web server exits or the command line script is executed and exits) (MSHUTDOWN, corresponding to MINIT).

<span>PHP_RSHUTDOWN_FUNCTION(myphpextension)
{
    </span><span>//</span><span> 例如记录请求结束时间，并把相应的信息写入到日志文件中</span>
    <span>return</span><span> SUCCESS;
}</span>

(2) Single-process SAPI life cycle

CLI/CGI mode PHP belongs to the single-process SAPI mode. This type of request is closed after processing the request once. SAPI life cycle: start-request start-request close-end

(3) Multi-process SAPI life cycle

Usually PHP is compiled into a module of Apache. Apache usually adopts multi-process mode. After Apache is started, it will fork multiple child processes. Each process has an independent memory space. Each child process will go through the start and end stages, but each The initial phase of the process only occurs after the process forks out, and it may be possible to process multiple requests during the entire process life cycle. The shutdown phase is only performed after Apache is shut down or the process is terminated. In these two phases, the request will be repeated with each request - the request shutdown link

(4) The multi-thread mode is similar to a process in a multi-process. The difference is that the request start-request closure process will be repeated in parallel throughout the life cycle of the process.

3. Zend Engine

Zend engine is the core of PHP implementation and provides the infrastructure for language implementation. For example, the implementation of PHP syntax, script compilation and running environment, expansion mechanism and memory management, etc. PHP here refers to the official PHP implementation (there is also Facebook's Hiphop, which has now developed into HHVM. So far (this project) PHP does not have a standard language specification), while PHP provides request processing and other Web server interface (SAPI)

http://www.bkjia.com/PHPjc/1095119.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/1095119.htmlTechArticleIn-depth understanding of the PHP kernel (2) Overview - PHP life cycle and Zend engine, -phpzend This article refers to "In-depth understanding PHP Kernel", address: https://github.com/reeze/tipi 1. SAPI interface SAPI (Serve...