"DHT Sensor Read Failed" in the Arduino IDE Serial Monitor.

[Nuba123]

I connected the DHT11 data pin (2) to ESP8266's D2 (GPIO 4) and define in sketch #define DHTPIN 4 for sending the temperature and humidity data to Firebase.
Following is the script.
#include <ArduinoJson.h>
#include <ESP8266WiFi.h>
#include <FirebaseArduino.h>
#include <DHT.h>
//#include <ESP8266HTTPClient.h>
//#include <SoftwareSerial.h>
#include <Adafruit_Sensor.h>
#define FIREBASE_HOST "yourproject.firebaseio.com"
#define FIREBASE_AUTH "000000000000000000000"
#define WIFI_SSID "MMMM"
#define WIFI_PASSWORD "XXXXXXXXXi"
#define DHTPIN 4
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
void setup() {
Serial.begin(115200);
delay(1000);
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
Serial.print("Connecting to ");
Serial.print(WIFI_SSID);
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(500);
}
Serial.println();
Serial.print("Connected to ");
Serial.println(WIFI_SSID);
Serial.print("IP Address is : ");
Serial.println(WiFi.localIP());
Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);
dht.begin();
}
void loop() {
float h = dht.readHumidity();
float t = dht.readTemperature();
if (isnan(h) || isnan(t)) {
Serial.println(F("Failed to read from DHT sensor!"));
return;
}

Serial.print("Humidity: ");
Serial.print(h);
String fireHumid = String(h) + String("%");
Serial.print("% Temperature: ");
Serial.print(t); Serial.println("°C ");
String fireTemp = String(t) + String("°C");
delay(4000);
Firebase.pushString("xxxx.firebaseio.com/DHT11/Humidity", fireHumid);
Firebase.pushString("xxxx.firebaseio.com/DHT11/Temperature", fireTemp);
}

And I also tried in another way. I installed the DHT11-master library. If I work with this library then I have to change some code logic which I write down above. if I run this code including dht11 library then its showing the error in the below line.
float h= dht.readHumidity();
float t = dht.readTemperature();

'class dht11' has no member named 'readHumidity'
Can anyone please help me to re-write the code to work?