#include <ESP8266WiFi.h>

const char* ssid = "vathsal";
const char* password = "1234567890";

const char* host = "wwwkprstaffcom.000webhostapp.com";
const int ldr = A0;
int val = 0;
String data;
void setup()
{
  Serial.begin(9600);
  Serial.println();

  Serial.printf("Connecting to %s ", ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println(" connected");
}


void loop()
{
  val = analogRead(ldr);
  data = "ldr=";

data.concat(val);
  WiFiClient client;

  Serial.printf("\n[Connecting to %s ... ", host);
  if (client.connect(host, 80))
  {
    Serial.println("connected]");
      client.println("POST /add.php HTTP/1.1");
client.println("Host: wwwkprstaffcom.000webhostapp.com");
client.println("Content-Type: application/x-www-form-urlencoded");
client.print("Content-Length: ");
client.println(data.length());
client.println();
client.print(data);
Serial.println(val);
    Serial.println("\n[Disconnected]");
  }
  else
  {
    Serial.println("connection failed!]");
    client.stop();
  }
  delay(5000);
}

My corrected code working code:

#include <ESP8266WiFi.h>

const char* ssid = "vathsal";
const char* password = "1234567890";

const char* host = "wwwkprstaffcom.000webhostapp.com";
const int ldr = A0;
int val = 0;
String data;
void setup()
{
  Serial.begin(9600);
  Serial.println();

  Serial.printf("Connecting to %s ", ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println(" connected");
}


void loop()
{
  val = analogRead(ldr);
  data = "ldr=";

  data.concat(val);
  WiFiClient client;

  Serial.printf("\n[Connecting to %s ... ", host);
  if (client.connect(host, 80))
  {
    Serial.println("connected]");
    client.println("POST /add.php HTTP/1.1");
    client.println("Host: wwwkprstaffcom.000webhostapp.com");
    client.println("Content-Type: application/x-www-form-urlencoded");
    client.print("Content-Length: ");
    client.println(data.length());
    client.println();
    client.print(data);
    Serial.println(val);
    Serial.println("\n[Disconnected]");
  }
  else
  {
    Serial.println("connection failed!]");
    client.stop();
  }
  delay(5000);
}