Back button with FormIt / FormItRetriever

[[!FormIt? &hooks=`redirect` &store=`1` &redirectTo=`30`]]
[[!FormItRetriever]]

<form class="form" action="[[~[[*id]]]]" method="post">
<input type="hidden" name="naam" value="[[!+fi.naam]]" />	
	<label for="content">
	        Reactie:
	        <span class="error">[[+fi.error.content]]</span>
	    </label>
	    <textarea id="reactie" cols="55" rows="7" name="reactie:required:stripTags">[[!+fi.reactie]]</textarea>
	
	<div class="form-buttons">
		<input type="submit" value="Verder!" />
	</div>
</form>

[[!FormIt? &hooks=`backOrForward` &store=`1`]]
[[!FormItRetriever]]

<form class="form" action="[[~[[*id]]]]" method="post"><input type="hidden" name="nospam:blank" /> <input type="hidden" name="resource_id" value="[[!+fi.id]]" /> 
<input type="hidden" name="genomineerde_id" value="[[!+fi.genomineerde_id]]" />
<input type="hidden" name="reactie_id" value="[[!+fi.reactie_id]]" />


<label for="naam"> Naam: <span class="error">[[+fi.error.naam]]</span> </label> 
<input id="naam" type="text" name="naam:required" value="[[!+fi.naam]]" />

<div class="form-buttons">
<input type="submit" name="previous" value="Terug!" />
<input type="submit" name="next" value="Verder!" />
</div>

</form>

$modx->log(modX::LOG_LEVEL_ERROR,'START BACK OR F0RWARD');

if (isset($_POST['next'])) {
 $modx->log(modX::LOG_LEVEL_ERROR,'next clicked');
	$url = $modx->makeUrl(31);
	$modx->sendRedirect($url);
} else if (isset($_POST['previous'])) {
 $modx->log(modX::LOG_LEVEL_ERROR,'previous clicked');
	$url = $modx->makeUrl(22);
	$modx->sendRedirect($url);
} else {
 $modx->log(modX::LOG_LEVEL_ERROR,'nothing clicked');
	$url = $modx->makeUrl(100);
	$modx->sendRedirect($url);
}

    /**
     * Gets a unique session-based store key for storing form submissions.
     *
     * @return string
     */
    public function getStoreKey() {
        return $this->modx->context->get('key').'/elements/formit/submission/'.md5(session_id());
    }

    /**
     * Handle post-processing through postHooks
     * @return bool
     */
    public function postProcess() {
        $success = $this->runPostHooks();
        if ($success) {
            /* if store is set for FormItRetriever, store fields here */
            $store = $this->modx->getOption('store',$this->config,false);
            if (!empty($store)) {
                $this->dictionary->store();
            }

            /* if the redirect URL was set, redirect */
            $this->checkForRedirect();

            /* set success placeholder */
            $this->setSuccessMessage();

            /* if clearing fields on success, just end here */
            if ($this->modx->getOption('clearFieldsOnSuccess',$this->config,true)) {
                $this->clearFieldsAtEnd = true;
            }
        }

        return $success;
    }