<?php
include("db.php");

if (isset($_POST['username']) &&
    isset($_POST['password']) &&
    isset($_POST['email']))
{
  //Prevent SQL injections
  $username = mysql_real_escape_string($_POST['username']);
  $email = mysql_real_escape_string($_POST['email']);

  //Get MD5 hash of password
  $password = md5($_POST['password']);

  //Check to see if username exists
  $sql = mysql_query("SELECT username FROM usersystem WHERE username = 'username'");

  if (mysql_num_rows($s > 0))
  {
    die ("Username taken.");
  }

  mysql_query("INSERT INTO usersystem (username, password, email) VALUES ( '$username', '$password', '$email')")
    or die (mysql_error()); echo "Account created.";
}
?>

<?php
session_start();
mysql_connect("localhost", "mydatabase", "mypassword");
mysql_select_db("ratherda_jetpackfandango");

function user_login ($username, $password)
{
  //take the username and prevent SQL injections
  //$username = mysql_real_escape_string($username);

  //begin the query
  $sql = mysql_query("SELECT * FROM user WHERE username = 'username' AND password = 'password' LIMIT 1");

  //check to see how many rows were returned
  $rows = mysql_num_rows($sql);

  if ($rows<=0 )
  {
    echo "Incorrect username/password";
  }
  else
  {
    //have them logged in
    $_SESSION['username'] = $username;
  }
}
?>

<?php

session_start();

require_once("db.php");