How can resolv this bugg in PHP (login area)?

Hi!

I am starting developing with PHP.

I need to understand what happen in my codes when I need to get in my login area. Everything its works (when I need to login with the correct username and password. Its display it me a error message:

Fatal error: Call to undefined function session_register() in C:\xampp\htdocs\checklogin.php on line 32

See in order what I do:

main_loging.php

Member Login
Username	:
Password	:

-----

chechlogin.php

$host="localhost"; // Host name

$username=""; // Mysql username

$password=""; // Mysql password

$db_name="test"; // Database name

$tbl_name="members"; // Table name

// Connect to server and select databse.

mysql_connect("$host", "$username", "$password")or die("cannot connect");

mysql_select_db("$db_name")or die("cannot select DB");

// username and password sent from form

$myusername=$_POST['myusername'];

$mypassword=$_POST['mypassword'];

// To protect MySQL injection (more detail about MySQL injection)

$myusername = stripslashes($myusername);

$mypassword = stripslashes($mypassword);

$myusername = mysql_real_escape_string($myusername);

$mypassword = mysql_real_escape_string($mypassword);

$sql="SELECT * FROM members WHERE username='$myusername' and password='$mypassword'";

$result=mysql_query($sql);

// Mysql_num_row is counting table row

$count=mysql_num_rows($result);

// If result matched $myusername and $mypassword, table row must be 1 row

if($count==1){

// Register $myusername, $mypassword and redirect to file "login_success.php"

session_register("myusername");// Its buggs here number 32

session_register("mypassword");

header("location:login_success.php");

}

else {

echo "Wrong Username or Password";

}

------------

login_success.php

// Check if session is not registered, redirect back to main page.

// Put this code in first line of web page.

session_start();

if(!session_is_registered(myusername)){

header("location:main_login.php");

}

------------

logout.php

session_start();

session_destroy();