My form won't work within my bootstrap - php

Question

I've written code to make a login page, this worked fine. However when I implemented it into my modified bootstrap-template, it wouldn't work anymore.
edit: it will just not give any result, if I understand firebug correctly the submit button does work but the rest of it doesn't, (atleast, it gives me an output in the firebug console) it doesn't seem to send a username or password, and it does sertainly not redirect me to the page set in action=" "
Here is my code:
<div id="login" class="container" style="color:#f7f7f7; background-color:#222222">
<div class="row">
<div class="col-lg-12 text-center">
<h2 class="section-heading">Login</h2>
</div>
</div>
<div class="row text-center">
<div class="col-md-4 col-md-offset-4">
<form method="POST" action="passwordunhash.php">
<p> username: <input type="text" name="username" value="username"></p>
<p> password: <input type="password" name="password" value=""></p>
<p> <input type="submit" value="Inloggen"></p>
</form>
</div>
</div>
</div>
<?php
if (empty($_POST['username']) && empty($_POST['password']) ){
echo " ";
}
else {
$query = "SELECT rank FROM users WHERE username='$username'";
if (!$resultaat = mysql_query($query) ){
$boodschap .= "query \"$query \" mislukt";
// echo "Dit is de boodschap: ".$boodschap." einde boodschap ";
echo "username not found";
}
else {
$rij = mysql_fetch_array($resultaat);
$_SESSION['rank'] = $rij["rank"];
}
$query = "SELECT password FROM users WHERE username='$username'";
if (!$resultaat = mysql_query($query) ){
$boodschap .= "query \"$query \" mislukt";
// echo "Dit is de boodschap: ".$boodschap." einde boodschap ";
echo "username not found";
}
$rij = mysql_fetch_array($resultaat);
$hash = $rij["password"];
if (password_verify($password, $hash)){
$_SESSION['loggedin'] = true;
header("Location: /index.php");
exit();
}
else {
echo 'username or password is incorrect';
session_unset();
session_destroy();
}
}
?>
this is the part I think the problem should be in.
I tried various things, including using the bootstrap form functions and leaving the action blank.
Sorry for the dutch words in it.
This is also my first question on stackoverflow, so if I missed any critical info you might need, please tell me.