Ошибка mysql_fetch_array

<?php
require_once("db.php");
if($F['boy']==0)
{
echo '<a href="loc.php">Вы не в бою</a>';
}
if(isset($_GET['monster']))
{
$f['boy'] = 1;
mysql_query("update users set boy='1' where login='" . $f['login'] . "'");
$hod = 0;
$position = 20;
$perem = 1;
$log = "";
}
if($position < 0) $position = 0;
if($position > 20) $position = 20;
if($_GET['hod'] == 1)
{
$hod = 1;
unset($_GET['hod']);
}
$mres = mysql_query("select * from monsters where id='" . $_GET['monster'] . "'");
$mon = mysql_fetch($mres);
if($perem = 1)
{
unset($perem);
$mhp = $mon['hp'];
$mposition = $mon['position'];
}
if($mposition < 0) $mposition = 0;
if($mposition > 20) $mposition = 20;
if($f['hp'] <= 0)
{
exit('<a href="loc.php">Враг убил вас!</a>');
$f['boy'] = 0;
mysql_query("update users set boy='0' where login='" . $f['login'] . "'");
}
if($mhp <= 0)
{
exit('<a href="loc.php">Вы убили врага</a>');
$f['boy'] = 0;
mysql_query("update users set boy='0' where login='" . $f['login'] . "'");
}
echo '<a href="battle.php">[Обновить] </a>';
echo '<a href="battle.php?hod=1">[Ход]</a><br/>';
echo 'HP: ' . $f['hp'] . '/' . $f['maxhp'] . ' П:' . $position . '<br/>';
echo 'П:' . $mposition . ' ' . $mon['name'] . ' n/a ' . $mhp . '/' . $mon['maxhp'] . '<br/>';
if($position == $mposition) echo '<a href="battle.php?bit=1">Бить</a><br/>';
if($position == 1)
{
echo '<a href="battle.php?pos=2">' . $position - 1 . '</a> ';
echo $position;
}
elseif($position == 0) echo $position;
else
{
echo '<a href="battle.php?pos=1">' . $position - 2 . '</a> ';
echo '<a href="battle.php?pos=2">' . $position - 1 . '</a> ';
echo $position;
}
echo '<br/';
echo $log;
echo '<br/>';
//Сами действия
if($hod = 1)
{
$hod = 0;
if($mposition != $position)
{
$mposition++;
$log .= $mon['name'] . " Подходит ближе к " . $f['login'] . "<br/>";
}
if($mposition == $position)
{
$f['hp'] - 5;
mysql_query("update users set hp='" . $f['hp'] . "' where login='" . $f['login'] . "'");
$log .= $mon['name'] . " наносит удар в корпус " . $f['login'] . " на 5<br/>";
}
}
if($_GET['pos'] == 1)
{
$hod = 1;
$position - 2;
$log .= $f['login'] . " идет на " . $position . "<br/>";
}
if($_GET['pos'] == 2)
{
$hod = 1;
$position--;
$log .= $f['login'] . " идет на " . $position . "<br/>";
}
if($_GET['bit'] == 1)
{
$hod = 1;
unset($_GET['bit']);
$mhp - 10;
$log .= $f['login'] . " наносит удар в корпус " . $mon['name'] . " на 10<br/>";
}