php gastenboek probleem

Hallo,
Ik heb een gastenboek op mijn site en in principe doet hij het, alleen bij het verversen van de pagina maakt hij weer een record in de database erbij. Hij gebruikt hierbij de laatst gebruikte gegevens. Ik kom er niet uit, wie helpt mij?

<form method="post" action="<?php echo($_server["PHP_SELF"]);?>" >
<font color = "996699" size = 3 face = verdana> Naam :</TD><TD> <input type="text" name="naam"><br></TD></TR>
<TR><TD>
<font color = "996699" size = 3 face = verdana> E-mail : </TD><TD> <input type="email" name="email"><br></TD></TR>
<TR><TD valign = "TOP">
<font color = "996699" size = 3 face = verdana> Bericht : </TD><TD><textarea name="commentaar" ROWS=6 COLS=50></textarea>
<br><br></TD></TR>
<TR><TD colspan = 2 align ="right">
<input type="submit" name="submit" value="Verzenden"></TD></TR>
</TABLE>


<?php
if(!empty($_post["submit"])){
include ("serverdata.php");

/* Make connection to database */
$db = mysql_connect($hostname, $username, $password) OR DIE("Unable to connect to database");

/* Select the database to be processed */
@mysql_select_db( "$dbName") or die( "Unable to select database");

$naam = $_POST["naam"];
$email = $_POST["email"];
$commentaar = $_POST["commentaar"];





$date=date("y-m-d");
$sql="INSERT INTO impression (naam, email, datum, commentaar) VALUES ('$naam', '$email', '$date', '$commentaar')";
mysql_query($sql, $db);
}

?>
<p>

<?php
include ("serverdata.php");

/* Make connection to database */
$db = mysql_connect($hostname, $username, $password) OR DIE("Unable to connect to database");

/* Select the database to be processed */
@mysql_select_db( "$dbName") or die( "Unable to select database");

$db = mysql_connect($hostname, $username, $password) OR DIE("Unable to connect to database");
$sql="SELECT * FROM impression ORDER BY ID DESC";
$res=mysql_query($sql, $db);

while ($ligne = mysql_fetch_object ($res))
{
print "<TABLE width = 80% border = 1 align = CENTER>";

print "<tr>";
print "<td width = 100 valign = top><font size = 2 color = 996699 face = verdana> Datum:br> $ligne->datum</td>";
print "<td rowspan = 3 valign = top> <font face = verdana size = 2>$ligne->commentaar</td></TR>";
print "<TR><td valign = top><font size = 2 color = 996699 face = verdana> Naam: <br> $ligne->naam </td></TR>";
print "<TR><td valign = top><font size = 3 color = 996699 face = verdana> E-mail:<br> $ligne->email </td>";

print "</tr>";
print "</TABLE>";
print "<p>";
}
mysql_free_result ($res);
mysql_close( $db);

?>