PHP Login

<?php
    session_start();

    // GET DATA

    $username=$_POST['uname'];
    $password=$_POST['passw'];
    $password=md5($password);

    // SELECT DATABASE
    $db = mysqli_connect('localhost', 'root' , '' , 'project');

    // CREATE QUERY
    $sql = "SELECT username, password FROM user_registration WHERE username = '$username' AND password = '$password'";

    $result = mysqli_query($db, $sql);

    if(mysqli_num_rows($result) > 0 ){
        echo "Correct Username and Password";

        $_SESSION['username'] = $username;


        header('location: welcome.php');

    } else {
        echo "Incorrect username and password";
    }

    mysqli_close($db);

?>