<?php
//checking if the script received a post request or not
if($_SERVER['REQUEST_METHOD']=='POST'){

 //Getting post data
 $name = $_POST['name'];
 $username = $_POST['username'];
 $password = $_POST['password'];
 $email = $_POST['email'];

 //checking if the received values are blank
 if($name == '' || $username == '' || $password == '' || $email == ''){
 //giving a message to fill all values if the values are blank
 echo 'please fill all values';
 }else{
 //If the values are not blank
 //Connecting to our database by calling dbConnect script
 require_once('dbConnect.php');

 //Creating an SQL Query to insert into database
 //Here you may need to change the retrofit_users because it is the table I created
 //if you have a different table write your table's name

 //This query is to check whether the username or email is already registered or not
 $sql = "SELECT * FROM ats WHERE username='$username' OR email='$email'";

 //If variable check has some value from mysqli fetch array
 //That means username or email already exist
 $check = mysqli_fetch_array(mysqli_query($con,$sql));

 //Checking check has some values or not
 if(isset($check)){
 //If check has some value that means username already exist
 echo 'username or email already exist';
 }else{
 //If username is not already exist
 //Creating insert query
 $sql = "INSERT INTO ats (name,username,password,email) VALUES('$name','$username','$password','$email')";

 //Trying to insert the values to db
 if(mysqli_query($con,$sql)){
 //If inserted successfully
 echo 'successfully registered';
 }else{
 //In case any error occured
 echo 'oops! Please try again!';
 }
 }
 //Closing the database connection
 mysqli_close($con);
 }
}else{
echo 'error';
}