toevoegen.php witte pagina

Deze vraag gaat waarschijnlijk over PHP

Hoi ik heb nu een fout in mijn script, als ik op submit druk krijg ik een witte pagina en zet hij niemand in de database...
kan iemand helpen?
<?php

if(file_exists('createadmin.php'))
{
exit("<h1>Loading error</h1>\n<p>You must delete <b>createadmin.php</b> first.</p>\n");
}

if($_POST['Submit']) {
// check email address
if ((!ereg(".+\@.+\..+", $email)) || (!ereg("^[a-zA-Z0-9_@.-]+$", $email))){
$error = "Invalid email address<br>";}

// display errors
if($error) {
?>

<b>Error</b><br>
<?php echo $error; ?><br>
<a href="#" onClick="history.go(-1)">try again</a> <?php }}
else {

if($_POST["username"] && $_POST["password"] && $_POST["email"]) {
include ("functie.php");

verbind();


$sql = "SELECT * FROM leden WHERE username LIKE '$username' ORDER BY id DESC";
$resultaat = mysql_query($sql) or die(mysql_error());

if ($row = mysql_fetch_object($resultaat)) {
echo "sorry deze gebruikers naam bestaat al";
}

else {

$sql = "INSERT INTO leden (username, password, email)
VALUES ('$username', '$password', '$email')";
mysql_query($sql) or die(mysql_error());
}

echo "succesvol toegevoegd<br><br>";
echo "<a href=\"login.php\">Inloggen</a>";

}
else {
?>

<form action="toevoegen.php" method="post">
<table border="1" cellspacing="0" cellpadding="0" bordercolor="#000000">
<tr><td>

<table border="0" cellspacing="0" cellpadding="5">
<tr><td class="dashed">Username:</td></tr>
<tr><td><input type="text" name="username" maxlength="15" size="15" /></td></tr>
<tr><td class="dashed">Password:</td></tr>
<tr><td><input type="password" name="password" maxlength="15" size="15" /></td></tr>
<tr><td class="dashed">E-mail:</td></tr>
<tr><td><input type="text" name="email" maxlength="15" size="15" /></td></tr>
<tr><td><input type="submit" name="Submit" value="Create" /></td></tr></table>

</td></tr>
</table>
</form>

<?php } }
?>

Display errors = on