php system

<?php
class register {
// MYSQL CONNECTION
function connect_db() {
 $connect = mysql_connect('localhost', 'root', '');
 if(!$connect)
  die ("Could not connect: " . mysql_error());
 else {
  mysql_query ("SET NAMES 'utf8'");
  mysql_query ("SET CHARACTER SET 'utf8'");
  mysql_query ("SET character_set_instance = 'utf8'");
  mysql_query ("utf8");
  mysql_select_db('my_db');
  }
 }

function registerNow() {
 if($_POST['register']) {

  $username = $_POST['username'];
  $password = $_POST['my_password'];
  $vpass = $_POST['valid_password'];
  $email = $_POST['email'];
  $terms = $_POST['terms'];

  // CHECKING IF USER EXISTS
  function userCheck() {
   global $username;
   $connect = connect_db();
   if (!$connect)
    die (mysql_error());
   else {
    $query = mysql_query("SELECT `username` FROM `userlist` WHERE `username`=" . $username);
    $fetch = mysql_fetch_row($query);
    if($fetch[0])
	 return true;
	else
	 return false;
   }
  }
  $usercheck = userCheck();

  // CHECKING IF EMAIL EXISTS
  function emailCheck() {
   global $email;
   $connect = connect_db();
   if (!$connect)
    die (mysql_error());
   else {
    $query = mysql_query("SELECT `email` FROM userlist WHERE `email`=" . $email);
    $fetch = mysql_fetch_row($query);
    if($fetch[0])
	 return true;
	else
	 return false;
   }
  }
  $emailcheck = emailCheck();

  // CHECKING IF PASSWORD IS TOO SHORT/TOO LONG
  function passwordStrlen() {
   global $password;
   $strlen = strlen($password);
   if($strlen > 12 OR $strlen < 5)
    return false;
   else
    return true;
  }
  $passwordstrlen = passwordStrlen();

  if(empty($username) OR empty($password) OR empty($email) OR empty($vpass) OR empty($terms))
   echo "You must fill out all inputs.";
  elseif($password != $vpass)
   echo "Password isn't valid";
  elseif($usercheck)
   echo "Username exists. Choose another.";
  elseif($emailcheck)
   echo "Email exists. Choose another.";
  elseif (!filter_var($email, FILTER_VALIDATE_EMAIL))
   echo "Email isn't valid.";
  elseif (!$passwordstrlen)
   echo "Password must be 5 to 12 characters.";
  else {
   $username = htmlspecialchars($username);
   $email = htmlspecialchars($email);
   $connect = connect_db();
   if (!$connect)
    die (mysql_error());
   else {
    mysql_query("INSERT INTO userlist(username, password, email) VALUES('" . $username . "', '" . $password . "', '" . $email . "')");
	echo "Dear " . $username . ", your details have been recieved, you are now registered to the system. please <a href='login.php'>login</a> so you can enjoy your features.";
   }
  }
 }
}
}

class login {
 $register = new register;
 $connect = $register->connect_db();

 if (!$connect)
  die (mysql_error());
 else {
   mysql_query ("SET NAMES 'utf8'");
   mysql_query ("SET CHARACTER SET 'utf8'");
   mysql_query ("SET character_set_instance = 'utf8'");
   mysql_query ("utf8");
   mysql_select_db('my_db');
 }
 function loginNow() {
  $username = $_POST['username'];
  $password = $_POST['password'];

    // CHECKING IF USER EXISTS (DIFFERENTLY)
  function isReal() {
   global $username;
   global $password;
   $connect = connect_db();
   if (!$connect)
    die (mysql_error());
   else {
    $query = mysql_query("SELECT `password` FROM `userlist` WHERE `username`=" . $username);
    $fetch = mysql_fetch_row($query);
    if($fetch[0] == $password)
	 return true;
	else
	 return false;
   }
  }
  $is_real = isReal();

  if (empty($username) OR empty($password))
   echo "You must fill out all inputs";
  elseif (!$is_real)
   echo "Username or password is wrong, try again";
  else {
   $username = htmlspecialchars($username);
   if ($connect) {
    setcookie("username", $username, time()+3600);
	setcookie("password", $password, time()+3600);
	session_start();
	$_SESSION['user'] = $_COOKIE['username'];
	mysql_close($connect);
	echo "You are now logged in to the system";
   }
  }
 }
 function logoutNow() {
  if ($_GET['logout'] == 'yes') {
   unset($_COOKIE['username']);
   unset($_COOKIE['password']);
   setcookie("username", NULL, time()-3600);
   setcookie("password", NULL, time()-3600);
  }
 }
}
?>