add one rc522 to my program

Projects Programming
1

hello it's been 3 days that I try to add another rifd rc522 reader to my program but can't I get someone to help me ?
thank you here is my program

#define dht_apin 2 // Analog Pin sensor is connected t 
#include <dht.h>
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,20,4);
dht DHT;

#include <SPI.h>
#include <MFRC522.h> 
#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);
int val;
int relay = 7 ;

 
void setup(){
Serial.begin(9600);  
SPI.begin();
mfrc522.PCD_Init(); 
lcd.init();                     
lcd.backlight();
lcd.setCursor(0,0);
pinMode(relay,OUTPUT);

}
 
void loop(){
    
    val=digitalRead(relay);
    
    DHT.read11(dht_apin);
    lcd.println("humi");
    lcd.print(DHT.humidity);
    lcd.print("%  ");
    lcd.println("temp");
    lcd.print(DHT.temperature); 
    lcd.println("C  ");
    delay(800);


    
    if ( ! mfrc522.PICC_IsNewCardPresent()) 
  {
    return;
  }
 
    if ( ! mfrc522.PICC_ReadCardSerial()) 
  {
    return;
  }
    String content= "";
   
    for (byte i = 0; i < mfrc522.uid.size; i++) 
  {
     Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
     Serial.print(mfrc522.uid.uidByte[i], HEX);
     content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
     content.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
     content.toUpperCase();
     if (content.substring(1) ==  "76 EE 3B 1F")
  {
    Serial.println("Authorized access");
    digitalWrite (relay,HIGH);
     delay(1000);
  }   
     if (content.substring(1) ==  "AA 03 B3 C3")
  {
    Serial.println("Authorized access");
    digitalWrite (relay,LOW);
    
  }
 
 }
2

can you post the error and the code producing the error?

3

I have no error I just want to add a second rifd module to my program but I don't know how to do it?

4 
dht DHT2;

   DHT2.read11(dht_apin);
    lcd.print(DHT2.humidity);
    lcd.print(DHT2.temperature);
5

the lcd is just used to have the temperature of my cold room and to display it on the lcd

6

I want to do as in this tutorial
but with my program

https://www.arduinoplatform.com/arduino-project/rfid-door-lock-with-multiple-rfid-readers-for-arduino/