Question

is it possible to write a validator for a zend form, which checks if the user has the right to change a form field? Means the user sees the field, but if tries even without permission (no acl right), he receives an error message? subsequent this means a field is deactivated if the user is not permitted to change the field.

Answer 1

Your going to want to use Zend_Acl to check permissions. You will want something like this:

/** Application_Validate_HasEditRights::isValid()**/
public function isValid($value, $context = array())
{
    // Set in form or element using $this->setResource()
    $resource  = $this->_resource;
    // Set in form or element using $this->setPrivilege()
    $privilege = $this->_privilege;

    if ( empty($resource) || empty($privilege) ) {
        throw new Zend_Exception("Validator requires a resource and privilege");
    }

    // Set in form or element $this->setOriginalValue()
    $original  = $this->_originalValue;
    $isEdit = false;
    // Check if original matches new value
    if ($original != $value) {
        $isEdit = true;
    }
    /** Get ACL **/
    $acl  = new Zend_Acl();
    $acl->addRole('guest');
    $acl->addRole('administrator', 'guest');

    $acl->addResource('form');
    // $acl->allow('role', 'resource', array('privilege'));
    $acl->allow('guest','form', array('limited')); // arbitrary resource and privilege names
    $acl->allow('administrator','form', array('full-access'));

    // Get the role of the logged in user; this may be different from how you store it
    $role = Zend_Auth::getInstance()->getIdentity()->role;

    // Check if the role has access to this form
    if ( $isEdit && !$acl->isAllowed($role, $resource, $privilege) ) {
        // Set Error message
        $this->_error(self::INVALID_PRIVILEGES);
        return false;
    }

    return true;
}