First of all create a database and Run this sql query in Phpmyadmin then follow next steps...
CREATE TABLE IF NOT EXISTS `members` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) NOT NULL,
  `sign_up_date` datetime NOT NULL,
  `email` varchar(255) NOT NULL,
  `bio` text,
  `account_permissions` enum('a','b','c') DEFAULT NULL,
  `email_activation` enum('0','1') DEFAULT NULL,
  `password` varchar(255) NOT NULL,
  `lastlogin` datetime DEFAULT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
Now Make your web pages as....
....................................................................................
-------------------For SignUp---------------------
save this as 'signup.php'
<h3 align='center'>Signup for a New Account</h3>
<h4 align='center'>Please fill given details below:</h4>
<form id='regForm' name='regForm' method='post' action='registerit.php'>
    <table width='600' border='0' cellpadding='2' cellspacing='0' align='center'>
    
    <tr>
      <th>*Email </th>
      <td><input name='email' type='text' class='textfield' id='email' /></td>
    </tr>
    <tr>
      <th>*Username</th>
      <td><input name='username' type='text' class='textfield' id='username' /></td>
    </tr>
    <tr>
      <th>*Password</th>
      <td><input name='password' type='password' class='textfield' id='password' /></td>
    </tr>
    <tr>
      <th>*Confirm Password </th>
      <td><input name='cpassword' type='password' class='textfield' id='cpassword' /></td>
    </tr>
     <tr>
      <td> </td>
      <td><input type='submit' name='Register' value='Register' /></td>
    </tr>
  </table>
</form>
------------------------------------------------------------------------
Save this as registerit.php
<?php
define('DB_HOST', 'localhost');
define('DB_USER', 'YOUR_DATABASE_USERNAME');  //Change Username with Your
define('DB_PASSWORD', 'YOUR_DB_PASSWORD');    //Change Password with Your
define('DB_DATABASE', 'YOUR_DB_NAME');        //Change Database name with Your
mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
mysql_select_db(DB_DATABASE);
		$email = $_POST['email'];
		$username = $_POST['username'];
		$password = $_POST['password'];
		$cpassword = $_POST['cpassword'];
		$date=date('Y-m-d h-i-s A');
if($password==$cpassword)
{
$q = mysql_query("insert into members (email,username,password,sign_up_date) values('$email','$username','$password','$date')");
		if ($q)
		{
		echo "<h2>Registration Successfull</h2>
		<a href='index.php'> Click to Login</a>";
		}
		else
		{
		echo "Something wrong with Query";
		}
}
else
{
echo "<h3>Password Not Match</h3>
}
?>
---------------------------------------------------------------------------------
-------------------For Login---------------------
Save this as 'index.php'
<h3 align='center'>Login</h3>
<form id='loginForm' name='loginForm' method='post' action='loginit.php'>
    <table width='600' border='0' cellpadding='2' cellspacing='0' align='center'>
    
   
    <tr>
      <th>*Username</th>
      <td><input name='username' type='text' class='textfield' id='username' /></td>
    </tr>
    <tr>
      <th>*Password</th>
      <td><input name='password' type='password' class='textfield' id='password' /></td>
    </tr>
   
     <tr>
      <td> </td>
      <td><input type='submit' name='Login' value='Login' /></td>
    </tr>
  </table>
</form>		
--------------------------------------------------
Save this as loginit.php
<?php
define('DB_HOST', 'localhost');
define('DB_USER', 'YOUR_DATABASE_USERNAME');  //Change Username with Your
define('DB_PASSWORD', 'YOUR_DB_PASSWORD');    //Change Password with Your
define('DB_DATABASE', 'YOUR_DB_NAME');        //Change Database name with Your
mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
mysql_select_db(DB_DATABASE);
session_start();
	
		$username = $_POST['username'];
		$password = $_POST['password'];
		$sql = mysql_query("SELECT * FROM members where username='$username' && password='$password'");
		if(mysql_num_rows($sql)==1)
		{
			session_regenerate_id();
			$member = mysql_fetch_assoc($sql);
			$_SESSION['SESS_MEMBER_ID'] = $member['id'];
			$_SESSION['SESS_EMAIL'] = $member['email'];
			$_SESSION['SESS_USERNAME'] = $member['username'];
			session_write_close();
			header("location: logged.php");
			
		}else {
			
			echo "Username Password Not Matched";
			
		}
		?>
-----------------------------------------------------------------------------------------
Save this as 'logged.php'
<?php
	//Start session
	session_start();
	
	if($_SESSION['SESS_USERNAME'] == '') {
		header("location: access-denied.php");
		exit();
	}
        else
	{
	echo "Welcome $_SESSION[SESS_USERNAME] You are Logged in";
	echo "<br /><a href='logout.php'>Logout</a>";
	
	}
?>
---------------------------------------------------------
Save it as 'logout.php'
<?php
//Start session
	session_start();
	unset($_SESSION['SESS_MEMBER_ID']);
	unset($_SESSION['SESS_EMAIL']);
	unset($_SESSION['SESS_USERNAME']);
		//Unset the variables stored in session
	
echo "<h1>Logout </h1>
<p align='center'> </p>
<h4 align='center' class='err'>You have been logged out.</h4>";
?>
-----------------------------------------------------------
Save it as 'access-denied.php'
<?php
echo "<h3>Access Denied</h3>";
?>
-------------------------------------------------------------------------------------
I think that this will solve your problem... enjoy...