Comment the same again and again - php

Question

I am trying to make a comments section, where people can comment stuff on my webpage.
All the comments get to a database. Alle that works fine.
The only problem I have is, when i have commented some stuff and reload the webpage it comment the same thing again.
Is there a if statement or something to prevent this?
while ($info = mysql_fetch_array($result)){
echo '<div style="border-style: solid; border-color: #808080; border-width: thin">
<div style="width: 1%"><p style="font-size: 10px; margin: 0px">'.$info['Navn'].'</p></div>
<p>'.$info['Besked'].'</p>
</div>';
}
if (isset($_POST['navn']) && isset($_POST['besked']) && isset($_POST['submit'])) {
$navn2 = $_POST['navn'];
$besked2 = $_POST['besked'];
$data = "INSERT INTO `tester`.`davs` (`Navn`, `Besked`) VALUES ('$navn2', '$besked2');";
$resultalt = mysql_query($data);
if ($resultalt) {
echo "$resultat";
}else{
echo "$resultat";
}
mysql_close();
}
?>
<form action="database.php" method="post" id="commentform">
<label for="comment_author" class="required">Your name</label>
<input type="text" name="navn" id="comment_author" value="" tabindex="1" required="required">
<label for="comment" class="required">Your message</label>
<textarea name="besked" id="comment" rows="10" tabindex="4" required="required"></textarea>
<input type="hidden" name="comment_post_ID" value="1" id="comment_post_ID" />
<input name="submit" type="submit" value="Submit comment" />
</form>
my php code:
http://pastebin.com/bQ7c1MPD
my inputs:
http://pastebin.com/P9uc6Hhz

Answer 1

Use tokens in your HTML form:
<input type="hidden" name="token" value="<?=$_SESSION['token'] = uniqid(); ?>" />
This require this at the top of the PHP script (before any output):
session_start();
For validation:
if(isset($_POST['submit']) && $_POST['token'] == $_SESSION['token']))
Full code: PHP | Form