===Register====
<?php
require "conn.php";

$password = $_POST["password"];
$username = $_POST["username"];

//$password = "password";
//$username = "username";

$mysql_qry = "INSERT INTO UserData (username,password) VALUES ('$username','$password')";
if($conn->query($mysql_qry) === TRUE){

  echo "Insert Successful";

}else{

  echo "Error:" .$mysql_qry. "<br>" .$conn->error;
}
$conn->close();

?>

===Connect===
<?php
$db_name = "xxxxx";
$mysql_username = "xxxxx";
$mysql_password = "xxxxx";
$server_name = "xxxxx";
$conn = mysqli_connect($server_name, $mysql_username, $mysql_password,$db_name);
if ($conn) {
   echo "Connected successfully";
}
if (!$conn) {
   echo "no";
}
?>

===Login===

<?php
require "conn.php";
$user_name = $_POST["user_name"];
$user_pass = $_POST["password"];
//$user_name = "jimbo";
//$user_pass = "jimbo123";
$mysql_qry = "SELECT * FROM UserData WHERE username = '$user_name' AND password = '$user_pass';";
$result = mysqli_query($conn ,$mysql_qry);
if(mysqli_num_rows($result) > 0) {
echo "login success !!!!! Welcome user";
}
else {
echo "login not success";
}

?>