谈谈你对Zend SAPIs(Zend SAPI Internals)的理解

 */
static sapi_module_struct cgi_sapi_module = {
#if PHP_FASTCGI
 "cgi-fcgi",      /* name */
 "CGI/FastCGI",     /* pretty name */
#else
 "cgi",       /* name */
 "CGI",       /* pretty name */
#endif
 
 php_cgi_startup,    /* startup */
 php_module_shutdown_wrapper, /* shutdown */
 
 NULL,       /* activate */
 sapi_cgi_deactivate,   /* deactivate */
 
 sapi_cgibin_ub_write,   /* unbuffered write */
 sapi_cgibin_flush,    /* flush */
 NULL,       /* get uid */
 sapi_cgibin_getenv,    /* getenv */
 
 php_error,      /* error handler */
 
 NULL,       /* header handler */
 sapi_cgi_send_headers,   /* send headers handler */
 NULL,       /* send header handler */
 
 sapi_cgi_read_post,    /* read POST data */
 sapi_cgi_read_cookies,   /* read Cookies */
 
 sapi_cgi_register_variables, /* register server variables */
 sapi_cgi_log_message,   /* Log message */
 NULL,       /* Get request time */
 
 STANDARD_SAPI_MODULE_PROPERTIES
};

 static int php_cgi_startup(sapi_module_struct *sapi_module)
{
 if (php_module_startup(sapi_module, NULL, 0) == FAILURE) {
  return FAILURE;
 }
 return SUCCESS;
}

 static int sapi_cgi_deactivate(TSRMLS_D)
{
 /* flush only when SAPI was started. The reasons are:
  1. SAPI Deactivate is called from two places: module init and request shutdown
  2. When the first call occurs and the request is not set up, flush fails on
   FastCGI.
 */
 if (SG(sapi_started)) {
  sapi_cgibin_flush(SG(server_context));
 }
 return SUCCESS;
}

static inline size_t sapi_cgibin_single_write(const char *str, uint str_length TSRMLS_DC)
{
#ifdef PHP_WRITE_STDOUT
 long ret;
#else
 size_t ret;
#endif
#if PHP_FASTCGI
 if (fcgi_is_fastcgi()) {
  fcgi_request *request = (fcgi_request*) SG(server_context);
  long ret = fcgi_write(request, FCGI_STDOUT, str, str_length);
  if (ret <= 0) {
   return 0;
  }
  return ret;
 }
#endif
#ifdef PHP_WRITE_STDOUT
 ret = write(STDOUT_FILENO, str, str_length);
 if (ret <= 0) return 0;
 return ret;
#else
 ret = fwrite(str, 1, MIN(str_length, 16384), stdout);
 return ret;
#endif
}
static int sapi_cgibin_ub_write(const char *str, uint str_length TSRMLS_DC)
{
 const char *ptr = str;
 uint remaining = str_length;
 size_t ret;
 while (remaining > 0) {
  ret = sapi_cgibin_single_write(ptr, remaining TSRMLS_CC);
  if (!ret) {
   php_handle_aborted_connection();
   return str_length - remaining;
  }
  ptr += ret;
  remaining -= ret;
 }
 return str_length;
}

static char *sapi_cgibin_getenv(char *name, size_t name_len TSRMLS_DC)
{
#if PHP_FASTCGI
 /* when php is started by mod_fastcgi, no regular environment
  is provided to PHP. It is always sent to PHP at the start
  of a request. So we have to do our own lookup to get env
  vars. This could probably be faster somehow. */
 if (fcgi_is_fastcgi()) {
  fcgi_request *request = (fcgi_request*) SG(server_context);
  return fcgi_getenv(request, name, name_len);
 }
#endif
 /* if cgi, or fastcgi and not found in fcgi env
  check the regular environment */
 return getenv(name);
}

static int sapi_cgi_send_headers(sapi_headers_struct *sapi_headers TSRMLS_DC)
{
 char buf[SAPI_CGI_MAX_HEADER_LENGTH];
 sapi_header_struct *h;
 zend_llist_position pos;
 if (SG(request_info).no_headers == 1) {
  return SAPI_HEADER_SENT_SUCCESSFULLY;
 }
 if (cgi_nph || SG(sapi_headers).http_response_code != 200)
 {
  int len;
  if (rfc2616_headers && SG(sapi_headers).http_status_line) {
   len = snprintf(buf, SAPI_CGI_MAX_HEADER_LENGTH,
       "%s\r\n", SG(sapi_headers).http_status_line);
   if (len > SAPI_CGI_MAX_HEADER_LENGTH) {
    len = SAPI_CGI_MAX_HEADER_LENGTH;
   }
  } else {
   len = sprintf(buf, "Status: %d\r\n", SG(sapi_headers).http_response_code);
  }
  PHPWRITE_H(buf, len);
 }
 h = (sapi_header_struct*)zend_llist_get_first_ex(&sapi_headers->headers, &pos);
 while (h) {
  /* prevent CRLFCRLF */
  if (h->header_len) {
   PHPWRITE_H(h->header, h->header_len);
   PHPWRITE_H("\r\n", 2);
  }
  h = (sapi_header_struct*)zend_llist_get_next_ex(&sapi_headers->headers, &pos);
 }
 PHPWRITE_H("\r\n", 2);
 return SAPI_HEADER_SENT_SUCCESSFULLY;
 }

static int sapi_cgi_read_post(char *buffer, uint count_bytes TSRMLS_DC)
{
 uint read_bytes=0, tmp_read_bytes;
#if PHP_FASTCGI
 char *pos = buffer;
#endif
 count_bytes = MIN(count_bytes, (uint) SG(request_info).content_length - SG(read_post_bytes));
 while (read_bytes < count_bytes) {
#if PHP_FASTCGI
  if (fcgi_is_fastcgi()) {
   fcgi_request *request = (fcgi_request*) SG(server_context);
   tmp_read_bytes = fcgi_read(request, pos, count_bytes - read_bytes);
   pos += tmp_read_bytes;
  } else {
   tmp_read_bytes = read(0, buffer + read_bytes, count_bytes - read_bytes);
  }
#else
  tmp_read_bytes = read(0, buffer + read_bytes, count_bytes - read_bytes);
#endif
  if (tmp_read_bytes <= 0) {
   break;
  }
  read_bytes += tmp_read_bytes;
 }
 return read_bytes;
}

static char *sapi_cgi_read_cookies(TSRMLS_D)
{
 return sapi_cgibin_getenv((char *) "HTTP_COOKIE", sizeof("HTTP_COOKIE")-1 TSRMLS_CC);
}

static void sapi_cgi_register_variables(zval *track_vars_array TSRMLS_DC)
{
 /* In CGI mode, we consider the environment to be a part of the server
  * variables
  */
 php_import_environment_variables(track_vars_array TSRMLS_CC);
 /* Build the special-case PHP_SELF variable for the CGI version */
 php_register_variable("PHP_SELF", (SG(request_info).request_uri ? SG(request_info).request_uri : ""), track_vars_array TSRMLS_CC);
}

static void sapi_cgi_log_message(char *message)
{
#if PHP_FASTCGI
 if (fcgi_is_fastcgi() && fcgi_logging) {
  fcgi_request *request;
  TSRMLS_FETCH();
  request = (fcgi_request*) SG(server_context);
  if (request) {
   int len = strlen(message);
   char *buf = malloc(len+2);
   memcpy(buf, message, len);
   memcpy(buf + len, "\n", sizeof("\n"));
   fcgi_write(request, FCGI_STDERR, buf, len+1);
   free(buf);
  } else {
   fprintf(stderr, "%s\n", message);
  }
  /* ignore return code */
 } else
#endif /* PHP_FASTCGI */
 fprintf(stderr, "%s\n", message);
}