HTTP POST with NodeMCU module using Arduino IDE -

i have nodemcu wifi module , code in arduino ide. have have problem sending something, using post method , reading page. have php page returns 2 variables. code below:

#include <arduino.h> #include <esp8266wifi.h> #include <esp8266wifimulti.h> #include <esp8266httpclient.h> #define use_serial serial  esp8266wifimulti wifimulti; httpclient http;  void setup() {     use_serial.begin(115200);     // use_serial.setdebugoutput(true);     use_serial.println();     use_serial.println();     use_serial.println();      (uint8_t t = 4; t > 0; t--) {         use_serial.printf("[setup] wait %d...\n", t);         use_serial.flush();         delay(1000);     }     wifimulti.addap("ssid", "password"); }  void loop() {     // wait wifi connection      if ((wifimulti.run() == wl_connected)) {         httpclient http;         use_serial.print("[http] begin...\n");         // configure traged server , url         http.begin("http://server/test.php"); // http          http.addheader("content-type", "application/x-www-form-urlencoded");         http.post("id=s1&api=123456789");         http.writetostream(&serial);         http.end();          use_serial.print("[http] get...\n");         // start connection , send http header         int httpcode = http.get();          // httpcode negative on error         if (httpcode > 0) {             // http header has been send , server response header has been handled             use_serial.printf("[http] get... code: %d\n", httpcode);              // file found @ server             if (httpcode == http_code_ok) {                 string payload = http.getstring();                 use_serial.println(payload);             }         } else {             use_serial.printf("[http] get... failed, error: %s\n",                                                 http.errortostring(httpcode).c_str());         }          http.end();     }      delay(10000); } 

when run it, 411 error code. whats wrong here? how can solve it?
tested arguments in postman , ok.