Someone

<?php
 
class Pvac_Acl extends Zend_Acl
{
    public function __construct()
    {
        $config = Zend_Registry::get('config');             
        $roles = $config->acl->roles;
        $this->_addRoles($roles);
    }
    protected function _addRoles($roles)
    {
        foreach ($roles as $name=>$parents) {               
            if (!$this->hasRole($name)) {                   
                if (empty($parents)) {
                    $parents = null;
                } else {
                    $parents = explode(',', $parents);
                }
                $this->addRole(new Zend_Acl_Role($name), $parents);
            }
        }
    }
}