Logout script in PHP 5...

Have set them all with Session variables in php and maintain the 100% security in the entire web site effectively.

here are the example code blocks for checking the user table in mysql database.

session_start();

$host="localhost"; // Host name
$username="root"; // Mysql username
$password=""; // Mysql password
$db_name="lib_db"; // 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 $tbl_name WHERE username='$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:login_success.php");
}
else {
echo "Wrong Username or Password";
}
?>
}
?>

I have verified the log-out script also as follows.

session_start();
session_destroy();
header("location:main_login.php");
?>

How display Log-in success message:
 
// 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($_SESSION['myusername'])){
header("location:main_login.php");
}
?>;

Login Successful
session_start();
//echo $_SESSION['myusername'];
//echo $_SESSION['mypassword'];
?>