Apache的PHP模塊啟動

首先，了解一下每個Apache模塊都會輸出一個模塊數據結構，其定義結構如下（以PHP模塊為例）：

1. AP_MODULE_DECLARE_DATA module php5_module = {
2. STANDARD20_MODULE_STUFF,
3. create_php_config, /* create per-directory config structure */
4. merge_php_config, /* merge per-directory config structures */
5. NULL, /* create per-server config structure */
6. NULL, /* merge per-server config structures */
7. php_dir_cmds, /* command apr_table_t */
8. php_ap2_register_hook /* register hooks */
9. };

STANDARD20_MODULE_STUFF這個宏是必須的，這個宏在經過擴展以後，可以為編譯後的模塊載入服務器構建提供版本信息，在PHP的模塊中，create_php_config函數創建目錄配置結構，,merge_php_config合並目錄配置結構，php_dir_cmds函數為模塊配置相關指令，php_ap2_register_hook 注冊模塊的鉤子程序，對這個結構體會在apache的模塊中專門說明，在這裡主要關注的是php_ap2_register_hook.這裡定義的一些回調方法，會在Apache啟動的時候直接調用。

php_ap2_register_hook函數的實現在源碼sapi/apache2handler/sapi_apache2.c文件中：

1. void php_ap2_register_hook(apr_pool_t *p)
2. {
3. ap_hook_pre_config(php_pre_config, NULL, NULL, APR_HOOK_MIDDLE);
4. ap_hook_post_config(php_apache_server_startup, NULL, NULL, APR_HOOK_MIDDLE);
5. ap_hook_handler(php_handler, NULL, NULL, APR_HOOK_MIDDLE);
6. ap_hook_child_init(php_apache_child_init, NULL, NULL, APR_HOOK_MIDDLE);
7. }

php_apache_server_startup函數也在同一個文件裡面實現：

1. static int
2. php_apache_server_startup(apr_pool_t *pconf, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s)
3. {
4. void *data = NULL;
5. const char *userdata_key = "apache2hook_post_config";
7. /* Apache will load, unload and then reload a DSO module. This
8. * prevents us from starting PHP until the second load. */
9. apr_pool_userdata_get(&data, userdata_key, s->process->pool);
10. if (data == NULL) {
11. /* We must use set() here and *not* setn(), otherwise the
12. * static string pointed to by userdata_key will be mapped
13. * to a different location when the DSO is reloaded and the
14. * pointers won't match, causing get() to return NULL when
15. * we expected it to return non-NULL. */
16. apr_pool_userdata_set((const void *)1, userdata_key, apr_pool_cleanup_null, s->process->pool);
17. return OK;
18. }
20. /* Set up our overridden path. */
21. if (apache2_php_ini_path_override) {
22. apache2_sapi_module.php_ini_path_override = apache2_php_ini_path_override;
23. }
24. #ifdef ZTS
25. tsrm_startup(1, 1, 0, NULL);
26. #endif
27. sapi_startup(&apache2_sapi_module);
28. apache2_sapi_module.startup(&apache2_sapi_module);
29. apr_pool_cleanup_register(pconf, NULL, php_apache_server_shutdown, apr_pool_cleanup_null);
30. php_apache_add_version(pconf);
32. return OK;
33. }