typedef enum {
    NGX_HTTP_POST_READ_PHASE = 0,
 
    NGX_HTTP_SERVER_REWRITE_PHASE,
 
    NGX_HTTP_FIND_CONFIG_PHASE,
    NGX_HTTP_REWRITE_PHASE,
    NGX_HTTP_POST_REWRITE_PHASE,
 
    NGX_HTTP_PREACCESS_PHASE,
 
    NGX_HTTP_ACCESS_PHASE,
    NGX_HTTP_POST_ACCESS_PHASE,
 
    NGX_HTTP_TRY_FILES_PHASE,
    NGX_HTTP_CONTENT_PHASE,
 
    NGX_HTTP_LOG_PHASE
} ngx_http_phases;

NGX_HTTP_POST_READ_PHASE = 0       //读取请求阶段
NGX_HTTP_SERVER_REWRITE_PHASE    //URI转换阶段
NGX_HTTP_FIND_CONFIG_PHASE         //查找相应的配置来执行阶段
NGX_HTTP_REWRITE_PHASE               //URI转换阶段（不太清楚此处）
NGX_HTTP_POST_REWRITE_PHASE      //对转换后的URL结果进行处理的阶段
NGX_HTTP_PREACCESS_PHASE           //权限检查准备阶段
NGX_HTTP_ACCESS_PHASE                //权限检查阶段
NGX_HTTP_POST_ACCESS_PHASE       //对权限检查结果进行处理阶段
NGX_HTTP_TRY_FILES_PHASE            //处理配置中的try_files阶段
NGX_HTTP_CONTENT_PHASE             //处理生成返回数据阶段(此处认为不太细，当然有filter也可以忽略)
NGX_HTTP_LOG_PHASE                    //记录日志处理阶段，具体说明应当是请求完成后，关闭请求时处理

static ngx_int_t
ngx_http_xxx_init(ngx_conf_t *cf)
{
	ngx_http_handler_pt        *h;
	ngx_http_core_main_conf_t  *cmcf;
 
	cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);
 
	h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
	if (h == NULL) {
		return NGX_ERROR;
	}
 
	*h = ngx_http_xxx_handler;
 
	return NGX_OK;
}

NGX_OK                              //处理成功，进入下一阶段
NGX_DECLINED                     //放弃处理
NGX_AGAIN || NGX_DONE      //处理完成，返回该值会触发请求
NGX_ERROR || NGX_HTTP_..  //处理错误或者HTTP的其它状态值

static char *
ngx_http_xxx_server(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
	ngx_str_t                 *value;
	ngx_url_t                  u;
	ngx_http_core_loc_conf_t  *clcf;
 
	clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
 
	clcf->handler = ngx_http_xxx_handler;
 
	if (clcf->name.data[clcf->name.len - 1] == '/') {
		clcf->auto_redirect = 1;
	}
 
	return NGX_CONF_OK;
}