[Translation] [php extension development and embedded] Chapter 12 - PHP startup process
黄舟
Release： 2023-03-05 16:28:02
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Initiation, termination, and some of the points in between
In this book, you have learned more Use the MINIT function for the first time to perform initialization tasks when PHP loads your extended shared library. In Chapter 1 "The Life Cycle of PHP", you also learned three other startup/termination functions. The counterpart to MINIT is MSHUTDOWN, and there are also There is a pair of RINIT/RSHUTDOWN methods that are called when each page request starts and terminates.
Lifecycle
In addition to these four functions that are directly linked to the module structure, there are two functions that are used only in the thread environment and handle the starting and termination of each thread, as well as the storage space they use. Before starting, first set your Copy the PHP extension skeleton program to ext/sample4 in the PHP source tree. The code is as follows
##config.m4
PHP_ARG_ENABLE(sample4,
[Whether to enable the "sample4" extension],
[ enable-sample4 Enable "sample4" extension support])
if test $PHP_SAMPLE4 != "no"; then
PHP_SUBST(SAMPLE4_SHARED_LIBADD)
PHP_NEW_EXTENSION(sample4, sample4.c, $ext_shared)
fi
Copy after login
php_sample4.h
#ifndef PHP_SAMPLE4_H
/* Prevent double inclusion */
#define PHP_SAMPLE4_H
/* Define Extension Properties */
#define PHP_SAMPLE4_EXTNAME "sample4"
#define PHP_SAMPLE4_EXTVER "1.0"
/* Import configure options
when building outside of
the PHP source tree */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
/* Include PHP Standard Header */
#include "php.h"
/* Define the entry point symbol
* Zend will use when loading this module
*/
extern zend_module_entry sample4_module_entry;
#define phpext_sample4_ptr &sample4_module_entry
#endif /* PHP_SAMPLE4_H */
Be careful, each Both the startup and termination functions return SUCCESS when exiting. If one of these functions returns FAILURE, the engine considers the process to have failed and interrupts the execution of php.
Module Life Cycle
has been used many times in the previous chapters, so MINIT should be familiar to you. It is triggered when the module is first loaded into the process space. For single Requesting sapi such as CLI and CGI, or multi-threaded sapi such as apache2-worker, it is only executed once, because it does not involve fork.
For multi-process sapi, such as apache1, apache2- prefork, for multiple webserver processes through their mod_php instances. Each mod_php instance must load its own extension module, so MINIT will be executed multiple times, but it will still only be executed once for each process.
When the module is unloaded, the MSHUTDOWN method is called. At this time, all resources of the module (such as persistent memory blocks) will be released and returned to the operating system.
Engine-side features, such as classes, resource IDs, stream wrappers and filters, user space global variables, instructions in php.ini, these public resources are allocated and released during the INIT and SHUTDOWN phases of the module.
Theoretically, you don’t need to do the resource release work in the MSHUTDOWN phase, leaving it to the OS to do the implicit memory and file release. But in apache 1.3 When using your extension, you will notice an interesting phenomenon, apache will load mod_php, run MINIT in the process, then immediately unload mod_php, trigger the MSHUTDOWN method, and then load it again. Without the correct MSHUTDOWN stage, during the MINIT stage The initially allocated resources will be leaked.
Thread life cycle
In multi-threaded sapi, Sometimes it is necessary to allocate each thread its own independent resources, or track its own single request counter. For these special cases, a set of per-thread hooks exist, allowing them to be executed when the thread starts and terminates. A typical case is When a sapi like apache2-worker is started, it will spawn a dozen or more threads to handle concurrent requests.
REGISTER_LONG_CONSTANT(char *name, long lval, int flags)
REGISTER_DOUBLE_CONSTANT(char *name, double dval, int flags)
REGISTER_STRING_CONSTANT(char *name, char *value, int flags)
REGISTER_STRINGL_CONSTANT(char *name,
char *value, int value_len, int flags)
Core global space. is mainly used by the Zend engine in script compilation and the bottom layer of the kernel Use . during execution. It is rare to test these values directly in your extension. .
##PG()
##php
Global space.Most"core"php.ini directives map to phpOne or more elements in the global variable structure.For example:
PG(register_globals), PG(safe_mode) and PG(memory_limit)
FG()
##File global space
.Most filesI/O Or stream-related global variables are loaded into this structure and exposed through standard extensions .
Through the study of this chapter, you have learned some new but already familiar concepts, including internal thread-safe global variables, how to expose information such as constants, pre-initialized variables, super global variables, etc. to user space. Next In this chapter, you will learn how to define and parse directives in php.ini and associate them with the internal thread-safe global structures you have set up.
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