php version upgrade from 5.3 to 5.4.x which creates issue in login validation

Question

This code gives me Fatal error: Call to undefined function session_register() after php version upgrade please any one help me in this matter

    $host="localhost"; // Host name 
    $username=""; // Mysql username 
    $password=""; // Mysql password 
    $db_name=""; // Database name 
    $tbl_name=""; // 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 $tbl_name WHERE username='$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");
    session_register("mypassword"); 
        header("location:operator.php");
        }
        else {
        header("location: http://");

        }
        ?>

This code for every target page operator.php Fatal error: Call to undefined function session_register()

<?php
session_start();
if(!session_register(myusername)){
header("location:login.html");
}

Answer 1

Change:

session_register("myusername");

to:

$_SESSION["myusername"] = $myusername;

and similarly for all the other calls.

Answer 2

Instead of session_register

Try and use $_SESSION

session_register is depreciated: http://www.php.net//manual/en/function.session-register.php