Problém s funkcí UPDATE

<?php 
require "../connect.php"; 

$id = $_GET['id']; 

$sql = MySQL_Query("SELECT * FROM clanky WHERE ID = '$id'"); 
$radek = MySQL_Fetch_Array($sql); 

?> 
<center> 
<?php echo "<form ACTION=\"edit.php?id=".$id."\" METHOD=\"POST\">" ?> 
<table CELLSPACING="0" CELLPADDING="2" > 
<tr><td>Name:<td><input TYPE="text" NAME="name" SIZE="28" STYLE="border: 1px solid black;" VALUE="<?php echo $radek['name'] ?>"></td> 
<tr><td>Date:<td><input TYPE="text" NAME="date" SIZE="28" STYLE="border: 1px solid black;" VALUE="<?php echo $radek['date']  ?>">   </td>
<tr><td>By:<td><input TYPE="text" NAME="by" SIZE="28" STYLE="border: 1px solid black;" VALUE="<?php echo $radek['by']  ?>">             </td>
<tr ><td colspan="2"><textarea ROWS="5" COLS="70" NAME="txt" STYLE="border: 1px solid black;"><?php echo $radek['txt'] ?></textarea></td></tr> 
<tr><td><input TYPE="submit" VALUE="Uložit změny" name="edit" STYLE="border: 1px solid black;"></td></tr> 
</table> 
</form> 
<hr><br><br> 
</center> 

<?php 
$name = $_POST['name']; 
$date = $_POST['date']; 
$by = $_POST['by']; 
$txt = $_POST['txt'];               

if (isset($_POST['edit'])) { 
$edit = MySQL_Query("UPDATE clanky SET name = '$name', date = '$date', by = '$by', txt = '$txt' WHERE id = '$id' "); 
if(!$edit): 
echo mysql_error(); 
else: 
echo "Zpráva byla upravena."; 
endif; 
mysql_close(); 
} 
?>