custom fields in registration form prestashop 1.6

[d.iandoli75]

I'm updating a module for Prestashop 1.6,

and I need to add two text fields to Customer registration form, but I didn't succeed in showing and updating data. 

here below some code from my module:

class Fattura24 extends Module{
 [...]
    public function install(){
[...]
//manually add new field in customer table
        $sqlInstallCod = 'ALTER TABLE ' ._DB_PREFIX_.'customer ADD codice_destinatario VARCHAR(255) DEFAULT NULL';
        Db::getInstance()->execute($sqlInstallCod);
        $sqlInstallPec = 'ALTER TABLE ' ._DB_PREFIX_.'customer ADD pec VARCHAR(255) DEFAULT NULL';
        Db::getInstance()->execute($sqlInstallPec);
[...]
// register hooks   
        if (!parent::install() 
            || !$this->registerHook('displayCustomerAccountForm')
            || !$this->registerHook('displayCustomerIdentityForm')
            || !$this->registerHook('actionCustomerAccountAdd')
            || !$this->registerHook('actionValidateOrder')
            || !$this->registerHook('actionOrderStatusUpdate')
            || !$this->registerHook('actionOrderStatusPostUpdate'))
            return false;
[...]
        return true;
}

here below the hooks: 

public function hookDisplayCustomerAccountForm($params){
        
        $query = 'SELECT codice_destinatario,pec FROM '._DB_PREFIX_.'customer WHERE id_customer=\''.$params['id_customer'] . '\';';
        $results = Db::getInstance()->getRow($query);
        
        if ( $results ) {
        $cod = $results['cod'];
        $pec = $results['pec'];
        }       
        
        $this->context->smarty->assign('codice_destinatario', $cod);
        $this->context->smarty->assign('pec', $pec);
        return $this->display(__FILE__, 'hookDisplayCustomerAccountForm.tpl');
    } 

public function hookDisplayCustomerAccountForm($params){
        
        $idCustomer = $params['Customer']->id;
        $query = 'SELECT codice_destinatario,pec FROM '._DB_PREFIX_.'customer WHERE id_customer=\''.$idCustomer . '\';';
        $results = Db::getInstance()->getRow($query);
        
        if ( $results ) {
        $cod = $results['cod'];
        $pec = $results['pec'];
        }       
        
        $this->context->smarty->assign('codice_destinatario', $cod);
        $this->context->smarty->assign('pec', $pec);
        return $this->display(__FILE__, 'hookDisplayCustomerAccountForm.tpl');
    } 

    public function hookDisplayCustomerIdentityForm($params){

        $idCustomer = $params['Customer']->id;
        $query = 'SELECT codice_destinatario FROM '._DB_PREFIX_.'customer WHERE id_customer=\'' . $idCustomer . /*$order_id . */'\';';
        $this->trace("hookDisplayMyAccountBlockfooter",$params);
        $this->trace("id_customer",$params['id_customer']);
        
        $codice_destinatario = Db::getInstance(_PS_USE_SQL_SLAVE_)->getRow($query)['docIdOrderFattura24'];
            
        $this->trace("hookDisplayMyAccountBlockfooter",$params);
        $this->context->smarty->assign('codice_destinatario', $cod);
        $this->context->smarty->assign('pec', $pec);
        return $this->display(__FILE__, 'hookDisplayCustomerAccountForm.tpl');
    }
 
    /**
     * save customer pec and destination code in table
     */
    public function hookActionCustomerAccountAdd($params){

        $pec = Tools::getValue('pec', $pec);
        $codice_destinatario = Tools::getValue('codice_destinatario', $cod);
        $idCustomer = $params['newCustomer']->id;
        $this->trace("idCustomer", $idCustomer);
        
        $queryCodiceDestinatario = 'UPDATE ' . _DB_PREFIX_ . 'customer SET codice_destinatario=\'' . $codice_destinatario . '\' WHERE id_customer=\'' . $idCustomer . '\';';
        Db::getInstance()->Execute($queryCodiceDestinatario);
        $queryPec = 'UPDATE ' . _DB_PREFIX_ . 'customer SET pec=\'' . $pec . '\' WHERE id_customer=\'' . $idCustomer . '\';';
        Db::getInstance()->Execute($queryPec);
    }

Actually I'm able to save data when customer is at checkout, but I cannot display nothing when editing or updating data in My account. 

Here below the template:

<div class="form-group">
    <label for="codice_destinatario">{l s='Codice Destinatario' mod='fattura24'}</label>
    <input class="form-control" name="codice_destinatario" type="text" id="codice_destinatario" value={codice_destinatario}/>
</div>
<div class="form-group">
    <label for="pec">{l s='PEC' mod='fattura24'}</label>
    <input class="form-control" name="pec" type="text" id="pec" value={pec}/>
</div>

I see the input field, but I cannot neither see nor update its content.

Any idea to solve?

Thanks,

David