apache启动php模块,APache的PHP模块启动
首先，了解一下每个Apache模块都会输出一个模块数据结构，其定义结构如下(以PHP模块为例)：
AP_MODULE_DECLARE_DATA module php5_module = {
STANDARD20_MODULE_STUFF,
create_php_config, /* create per-directory config structure */
merge_php_config, /* merge per-directory config structures */
NULL, /* create per-server config structure */
NULL, /* merge per-server config structures */
php_dir_cmds, /* command apr_table_t */
php_ap2_register_hook /* register hooks */
};
STANDARD20_MODULE_STUFF这个宏是必须的，这个宏在经过扩展以后，可以为编译后的模块载入服务器构建提供版本信息，在PHP的模块中，create_php_config函数创建目录配置结构，,merge_php_config合并目录配置结构，php_dir_cmds函数为模块配置相关指令，php_ap2_register_hook 注册模块的钩子程序，对这个结构体会在apache的模块中专门说明，在这里主要关注的是php_ap2_register_hook.这里定义的一些回调方法，会在Apache启动的时候直接调用。
php_ap2_register_hook函数的实现在源码sapi/apache2handler/sapi_apache2.c文件中：
void php_ap2_register_hook(apr_pool_t *p)
{
ap_hook_pre_config(php_pre_config, NULL, NULL, APR_HOOK_MIDDLE);
ap_hook_post_config(php_apache_server_startup, NULL, NULL, APR_HOOK_MIDDLE);
ap_hook_handler(php_handler, NULL, NULL, APR_HOOK_MIDDLE);
ap_hook_child_init(php_apache_child_init, NULL, NULL, APR_HOOK_MIDDLE);
}
php_apache_server_startup函数也在同一个文件里面实现：
static int
php_apache_server_startup(apr_pool_t *pconf, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s)
{
void *data = NULL;
const char *userdata_key = "apache2hook_post_config";
/* Apache will load, unload and then reload a DSO module. This
* prevents us from starting PHP until the second load. */
apr_pool_userdata_get(&data, userdata_key, s->process->pool);
if (data == NULL) {
/* We must use set() here and *not* setn(), otherwise the
* static string pointed to by userdata_key will be mapped
* to a different location when the DSO is reloaded and the
* pointers won't match, causing get() to return NULL when
* we expected it to return non-NULL. */
apr_pool_userdata_set((const void *)1, userdata_key, apr_pool_cleanup_null, s->process->pool);
return OK;
}
/* Set up our overridden path. */
if (apache2_php_ini_path_override) {
apache2_sapi_module.php_ini_path_override = apache2_php_ini_path_override;
}
#ifdef ZTS
tsrm_startup(1, 1, 0, NULL);
#endif
sapi_startup(&apache2_sapi_module);
apache2_sapi_module.startup(&apache2_sapi_module);
apr_pool_cleanup_register(pconf, NULL, php_apache_server_shutdown, apr_pool_cleanup_null);
php_apache_add_version(pconf);
return OK;
}在这个函数里会调用apache2_sapi_module.startup函数，而这个函数在前一篇博文
PHP内核-Apache2的SAPI 可以看到，它最终调用的是php_module_startup函数，
该函数在PHP的主要文件main/main.c文件中：
int php_module_startup(sapi_module_struct *sf, zend_module_entry *additional_modules, uint num_additional_modules)
{
zend_utility_functions zuf;
zend_utility_values zuv;
int module_number=0; /* for REGISTER_INI_ENTRIES() */
char *php_os;
#ifdef ZTS
zend_executor_globals *executor_globals;
void ***tsrm_ls;
php_core_globals *core_globals;
#endif
#if defined(PHP_WIN32) || (defined(NETWARE) && defined(USE_WINSOCK))
WORD wVersionRequested = MAKEWORD(2, 0);
WSADATA wsaData;
#endif
....................
php_ini_register_extensions(TSRMLS_C);
zend_startup_modules(TSRMLS_C);
/* disable certain classes and functions as requested by php.ini */
php_disable_functions(TSRMLS_C);
php_disable_classes(TSRMLS_C);
/* start Zend extensions */
zend_startup_extensions();
#ifdef ZTS
zend_post_startup(TSRMLS_C);
#endif
module_initialized = 1;
sapi_deactivate(TSRMLS_C);
module_startup = 0;
shutdown_memory_manager(1, 0 TSRMLS_CC);
/* we're done */
return SUCCESS;
}这时会对PHP做一些环境初始化，如：php_init_config会读取php.ini文件，根据这个文件的配置，初始化PHP的环境及控制变量。
这就完成从apache启动之后，至PHP的初始化和环境准备了。