<?php
session_start();
echo <<<HERE
Авторизация:
<form method="post" action="index.php?action=login">
login: <input type="text" name="login"><br \>
passwd: <input type="password" name="passwd"><br \>
<input type="submit" value="login"
HERE;
if ($_GET['action'] == "login") { loginuser(); }  
elseif ($_GET['action'] == "logchar") { logchar(); }  
elseif ($_GET['action'] == "game") { game(); }  
function loginuser() {
$login=$_POST['login'];
$password=$_POST['passwd'];
$result = mysql_query("SELECT * FROM users WHERE login='$login'");
$myrow = mysql_fetch_array($result);
if (empty($myrow['password']))
{
#login or passwd error reading
}
else {
if ($myrow['password']==$password) {  
$myid=$myrow['id'];
#valid
$chars=mysql_query("SELECT * FROM `chars` WHERE uid='$myid'");

     while($row=mysql_fetch_array($chars))
     {
  $id=$row['id'];
  $nickname=$row['nickname'];
  echo "<a href='index.php?action=logchar&id=$id'>$nickname</a>";
}
}
}
}
function logchar() {
$cid=$_GET['id'];
$rrrow=mysql_fetch_array(mysql_query("SELECT * FROM `chars` WHERE id='$cid'"));
$nickname=$rrrow['nickname'];
$_SESSION['CHAR']=$nickname;
#redirecting index.php?action=game
}
function game() {
  if (empty($_SESSION['CHAR']) {
  #redirecting index.php
  }
   else {
   #game
   }
}