universal login name
<?php

session_start();

$username = $_POST['username'];
$password = $_POST['password'];

if ($username&&$password)
{

$connect = mysql_connect("localhost","*i*****5_******","*******") or die ("Couldn't Connect"); //host,username,password
mysql_select_db("virtua15_gateway") or die ("Could not find database");

$query = mysql_query("SELECT * FROM Users WHERE username='$username'");
$numrows = mysql_num_rows($query);
if ($numrows!=0)
{
    while ($row = mysql_fetch_assoc($query))
    {
            $dbusername = $row['username'];
            $dbpassword = $row['password'];
    }
    if ($username==$dbusername&&md5($password)==$dbpassword)
    {
     header( 'Location: index2.php' );
     $_SESSION['username']=$dbusername;
    }
    else
        echo "incorrect username and password";
}
   else
     die ("This user does not exist");

}
else
    die("Please enter a username and a password")


?>

$username = strtolower($_POST['username']);

while ($row = mysql_fetch_assoc($query))
    {
            strtoupper($dbusername) = strtoupper($row['username']);
            $dbpassword = $row['password'];
    }

while ($row = mysql_fetch_assoc($query))
        {
                strtolower($dbusername) = strtolower($row['username']);
                $dbpassword = $row['password'];
        }

$username = $_POST['username'];
$query = mysql_query("SELECT * FROM Users WHERE username='$username'");

$username = mysql_real_escape_string($_POST['username']);
$password = mysql_real_escape_string($_POST['password']);

$query = mysql_query("SELECT * FROM Users WHERE username='$username'");

"SELECT * FROM Users WHERE username='$username' AND password='" . md5($password) . '"

if(mysql_num_rows($query)){
   // Login logic
}

mysql_query(
    "SELECT * FROM Users
         WHERE LOWER( username) = LOWER( '" . mysql_real_escape_string( $username) . "')"
);