$oldpassword = md5($_POST['oldpassword']);
$newpassword = md5($_POST['newpassword']);
$repnewpassword = md5($_POST['repnewpassword']);

$query3 = mysql_query("SELECT password FROM users WHERE username ='$username'") or die("Märkligt fel 1!");
$row2 = mysql_fetch_assoc($query3);
$oldpassworddb = $row2['password'];
if ($oldpassword == $oldpassworddb) {
    if ($newpassword == $repnewpassword) {
        $querychange1 = mysql_query("UPDATE users SET password='$newpassword' WHERE username='$username'");
        session_destroy();
        die("Lösenordet har ändrats");
    }
    else {
    die("Nya lösenordet matchar inte");
    }
}
else {
die("Märkligt fel 2!");
}