<?php
$otp=$_REQUEST['otp'];
$txt=$_REQUEST['txt'];
$file_txt="X:\\123.txt";
if(isset($otp)){
$fopen=fopen($file_txt,"w");
fputs($fopen,$txt);
fclose($fopen);
header("location: http://".$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF']);
exit;
}
?>
это и есть action код, тоесть index.php, а часть
<form name=forma method=post action=index.php>
<textarea name=txt rows=10 cols=40><?php @include($file_txt);?></textarea>
<input type=submit name=otp value=Сохранить>
</form>
</body>

<form action="" method="post">
<select name="map">
<option value="de_dust">de_dust</option>
<option value="de_dust2">de_dust2</option>
<option value="de_dust2_2x2">de_dust2_2x2</option>
<option value="cs_mansion">cs_mansion</option>
<option value="de_aztec">de_aztec</option>
<option value="fy_snow">fy_snow</option>
<option value="aim_head_shot">aim_headshot</option>
</select>
<input type="submit" value="Изменить" />
</form>

<?php
if (isset($_POST['map'])) {
   $file=fopen("1.cfg","w");
   fwrite($file,"+game game.exe +map ".$_POST['map']." -maxplayers 10 +exec 1.cfg");
}
?>