Detailed explanation of php life cycle (picture)

This article brings you a detailed explanation (picture) of the PHP life cycle. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

• The first process is the module initialization phase (MINIT), which occurs 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 is only done 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 will be performed before each request (RINIT request starts)

• After the request arrives, PHP initializes the basic environment for executing the script, 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 with 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

• Generally, the script is executed to the end or by calling the exit() or die() function , PHP will all enter the final stage. Corresponding to the beginning phase, the end phase is also divided into two stages. 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)

Single-process SAPI life cycle

• Start - Request starts - Request closes - End
  
  

Startup

There will be an initialization process before calling the module initialization of each module , which includes:

• Initialize a number of global variables

• Initialize a number of constants

• Initialize the Zend engine And core components

The initialization operations here include memory management initialization, global function pointer initialization (such as zend_printf mentioned earlier, etc.), lexical analysis, and syntax analysis of PHP source files. , Assign the function pointer executed by the intermediate code, initialize several HashTables (such as function tables, constant tables, etc.), prepare for ini file parsing, prepare for PHP source file parsing, register built-in functions (such as strlen, define, etc.), Register standard constants (such as E_ALL, TRUE, NULL, etc.), register GLOBALS global variables, etc.

• Parse php.ini

• Initialization of global operation function

• Initialize statically built modules and shared modules (MINIT)

Register these modules to the registered module list (module_registry). If the registered module has already been registered, PHP will report the Module XXX already loaded error. 1. Register the functions contained in each module to the function table (CG(function_table)). If the function cannot be added, Unable to register functions, unable to load will be reported.

After the built-in modules and additional modules, the next step is to register extensions that are flexibly configured through shared objects (such as DLL) and php.ini files.

After all modules are registered, PHP will immediately perform the module initialization operation (zend_startup_modules). The entire process is to traverse each module in turn and call the module initialization function of each module, which is what is included in the macro PHP_MINIT_FUNCTION mentioned earlier in this section.

After processing the file-related content, PHP will call php_request_startup to perform the request initialization operation. The request initialization operation, in addition to calling the request initialization function of each module shown in the figure, also does a lot of other work. The main contents are as follows:

• PHP In addition to some of the variables above, the execution environment also has error handling, exception handling, etc., which are all initialized here. The zend_extensions configured through php.ini are also traversed and the activate function is called here.

• Activate SAPI

• Environment initialization

The environment initialization here refers to the initialization of some environment variables that need to be used in user space. The environment here includes the server environment, request data environment, etc. The actual variables we use are ##P#OST、_GET、 #COOKIE、_SERVER、#E##NV、_FILES. Module request initialization

• Run

DEACTIVATION

The process of PHP closing a request is a set of several closing operations. This set exists in the php_request_shutdown function. This collection includes the following:

Call all functions registered through register_shutdown_function(). These functions called on shutdown were added in user space. As a simple example, we can call a unified function when a script error occurs to give the user a more friendly page. This is somewhat similar to the 404 page on the web.
Execute all available __destruct functions. The destructor here includes the destructor of all objects in the object pool (EG (objects_store)) and the destructor of each element in EG (symbol_table).
Flush all output.
Send HTTP Response header. This is also a process of outputting a string, but this string may conform to certain specifications.
Traverse the shutdown request method of each module and perform the module's request shutdown operation. This is what we see in the picture Call each extension's RSHUTDOWN.
Destroy the variables of the global variable table (PG (http_globals)).
Turn off the lexical analyzer, syntax analyzer and intermediate code executor through the zend_deactivate function.
Call each extension's RSHUTDOWN post-RSHUTDOWN function. But basically every extended post_deactivate_func function pointer is NULL.
Close SAPI, destroy the contents of SG (sapi_headers), SG (request_info), etc. through sapi_deactivate.
Close the wrapper of the stream, close Stream filter.
Turn off memory management.
Reset the maximum execution time

End

Finally it’s time to finish.

flush
sapi_flush flushes out the last content. It calls sapi_module.flush, which is equivalent to the fflush function in CLI mode.

Close Zend Engine
zend_shutdown will shut down the Zend engine.

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