login register php

<?php
if (!empty($_POST['login-submit']))
{
  $user=$_POST['user'];
  $pass=$_POST['pass'];
  $servername="localhost";
  $username="root";

   //create connection
  $conn=new mysqli($servername,$username,"","projectdb");
   //check connection
  if($conn->connect_error)
  {
    die("failed".$conn->connect_error);
  }

  $sql="SELECT user FROM users where (name='".$user."' OR email='".$user."') and password='".$pass."')";   // pro$

  if($conn->query($sql)===TRUE)
{
                echo "<html><h1>Welcome!</h1></html>";
  }
  else
  {
     echo "<html> <body> <h1>Hi!<h1></body></html>";
  }
  $conn->close();
}
if (!empty($_POST['register-submit']))
{
        //insert in table;sms on phn-otp;mail on id,pass confirm pass same
  echo "Thank you!<br>";
  $fname=$_POST["fname"];
  $lname=$_POST["lname"];
  $email=$_POST["email"];
  $user=$_POST["user"];
  $pass=$_POST["pass"];
  $cpass=$_POST["cpass"];
  $phn=$_POST["phn"];
  if($pass!=$cpass)
 {
          echo("Password not same.");
  }

//sms OTP

  //echo $name."<br>".$branch."<br>".$sex."<br>".$course."<br>".$contact."<br>".$emailid."<br>";
  $servername="localhost";
  $username="root";

   //create connection
   $conn=new mysqli($servername,$username,"","projectdb");
   //check connection
   if($conn->connect_error)
   {
     die("failed".$conn->connect_error);
   }
   //create database
   $sql="INSERT INTO users VALUES('".$fname."','".$lname."','".$email."','".$user."','".$pass."','".$phn."')";  //)",'".$_POST["column"]."')";
 if($conn->query($sql)===TRUE)
  {
    echo "You are successfully registered.<br><br>!";
  }
  else
  {
    echo "Some failure occured.";
  }
  $conn->close();
}