esconder form quando o valor é invalido

<div id="lostpw-text-top"><b><?php if(isset($stop)){

    echo "<p class='bg-danger'>$stop</p>";

     ?></b>  <p>You are on this page by mistake? Go to the <a href="http://www.google.com" target="_self"><b>login page.</a></b></p></div>

<div id="line"></div>


<? } else { ?>

<form role="form" method="post" action="" autocomplete="off">

<?php
// Verificar erros
if(isset($error)){
foreach($error as $error){
echo '<p class="bg-danger">'.$error.'</p>';
}
}

// Verificar a ação
switch ($_GET['action']) {
case 'active':
echo "Your account is now active you may now log in.";
break;
case 'reset':
echo "Please check your inbox for a reset link.";
break;
}
?>


<input type="password" name="password" id="password" class="form-control input-lg" placeholder="Password" tabindex="1">

<input type="password" name="passwordConfirm" id="passwordConfirm" class="form-control input-lg" placeholder="Confirm Password" tabindex="1">

<input type="submit" name="submit" value="Change Password" class="btn btn-primary btn-block btn-lg" tabindex="3">
</form>

<?php } ?>