创建tags 文件：
php-5.3.3 目录下：
ctags -R .
ctags -R -a -f tags ／path/to/httpd-2.2.16
如果需要tags使用绝对路径，则可以使用参数：
–tag-relative=no
1. mod_php.c的写法，主要是定义一些函数，然后通过模块结构体变量挂到apache的钩子上：
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//…
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// 1. 这个结构的名字php5_module是有严格要求的
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module MODULE_VAR_EXPORT php5_module =
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{
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STANDARD_MODULE_STUFF,
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php_init_handler, /* initializer */
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php_create_dir, /* per-directory config creator */
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php_merge_dir, /* dir merger */
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NULL, /* per-server config creator */
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NULL, /* merge server config */
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php_commands, /* command table */
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php_handlers, /* handlers */
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NULL, /* filename translation */
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NULL, /* check_user_id */
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NULL, /* check auth */
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NULL, /* check access */
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NULL, /* type_checker */
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NULL, /* fixups */
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NULL /* logger */
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#if MODULE_MAGIC_NUMBER >= 19970103
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, NULL /* header parser */
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#endif
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#if MODULE_MAGIC_NUMBER >= 19970719
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, NULL /* child_init */
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#endif
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#if MODULE_MAGIC_NUMBER >= 19970728
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, php_child_exit_handler /* child_exit */
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#endif
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#if MODULE_MAGIC_NUMBER >= 19970902
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, NULL /* post read-request *
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#endif
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};
2. apache模块结构的定义：
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typedef struct module_struct module;
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struct module_struct {
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/** API version, *not* module version; check that module is
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* compatible with this version of the server.
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*/
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int version;
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/** API minor version. Provides API feature milestones. Not checked
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* during module init */
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int minor_version;
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/** Index to this modules structures in config vectors. default -1*/
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int module_index;
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/** The name of the module’s C file */
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const char *name;
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/** The handle for the DSO. Internal use only ， default null*/
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void *dynamic_load_handle;
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/** A pointer to the next module in the list
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* @defvar module_struct *next ， default null*/
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struct module_struct *next;
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/** Magic Cookie to identify a module structure; It’s mainly
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* important for the DSO facility (see also mod_so). */
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unsigned long magic;
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/** Function to allow MPMs to re-write command line arguments. This
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* hook is only available to MPMs.
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* @param The process that the server is running in.
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*/
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void (*rewrite_args) (process_rec *process);
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/** Function to allow all modules to create per directory configuration
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* structures.
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* @param p The pool to use for all allocations.
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* @param dir The directory currently being processed.
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* @return The per-directory structure created
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*/
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void *(*create_dir_config) (apr_pool_t *p, char *dir);
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/** Function to allow all modules to merge the per directory configuration
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* structures for two directories.
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* @param p The pool to use for all allocations.
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* @param base_conf The directory structure created for the parent directory.
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* @param new_conf The directory structure currently being processed.
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* @return The new per-directory structure created
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*/
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void *(*merge_dir_config) (apr_pool_t *p, void *base_conf, void *new_conf);
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/** Function to allow all modules to create per server configuration
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* structures.
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* @param p The pool to use for all allocations.
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* @param s The server currently being processed.
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* @return The per-server structure created
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*/
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void *(*create_server_config) (apr_pool_t *p, server_rec *s);
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/** Function to allow all modules to merge the per server configuration
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* structures for two servers.
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* @param p The pool to use for all allocations.
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* @param base_conf The directory structure created for the parent directory.
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* @param new_conf The directory structure currently being processed.
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* @return The new per-directory structure created
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*/
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void *(*merge_server_config) (apr_pool_t *p, void *base_conf,
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void *new_conf);
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/** A command_rec table that describes all of the directives this module
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* defines. */
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const command_rec *cmds;
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/** A hook to allow modules to hook other points in the request processing.
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* In this function, modules should call the ap_hook_*() functions to
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* register an interest in a specific step in processing the current
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* request.
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* @param p the pool to use for all allocations
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*/
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void (*register_hooks) (apr_pool_t *p);
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};
3. apache动态加载模块的过程。 动态加载模块时，严格检查模块名，包括httpd.conf中的module name（如： php5_module）；对应的apache模块定义所在的文件的文件名（如： mod_php5.c）也是严格检查的。
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static const char *load_module(cmd_parms *cmd, void *dummy,
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const char *modname, const char *filename)
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{
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apr_dso_handle_t *modhandle;
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apr_dso_handle_sym_t modsym;
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module *modp;
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const char *szModuleFile = ap_server_root_relative(cmd->pool, filename);
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so_server_conf *sconf;
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ap_module_symbol_t *modi;
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//…
4. Apache conf 中的配置:
LoadModule php5_module modules/libphp5.so
5. apr 动态加载模块并获取指定符号（如：php5_module）：
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APR_DECLARE(apr_status_t) apr_dso_sym(apr_dso_handle_sym_t *ressym, apr_dso_handle_t *handle,
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const char *symname)
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{
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int err;
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if (symname == NULL)
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return APR_ESYMNOTFOUND;
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err = get_image_symbol(handle->handle, symname, B_SYMBOL_TYPE_ANY,
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ressym);
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if(err != B_OK)
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return APR_ESYMNOTFOUND;
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return APR_SUCCESS;
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}
6. 一切准备完毕后：
将模块写入已加载的模块列表中： ap_add_loaded_module(modp, cmd->pool);
注册相关钩子函数：
apr_pool_cleanup_register(cmd->pool, modi, unload_module, apr_pool_cleanup_null);
Finally we need to run the configuration process for the module
ap_single_module_configure(cmd->pool, cmd->server, modp);