Validation with variables

I've found this solution:

// validate data
$this->load->library('form_validation');
$validation_status = 1; // by default validation is ok
$fields_failed = array();

// EMAIL
if(!$this->form_validation->valid_email($email)){ //if email is not valid
$validation_status = 0;
array_push($fields_failed, "email");
}

if($validation_status){//no error in data, continue
$answer -> status = "1";
$answer -> message = "Tutti-frutti, validation is OK we can continue...";
} else {
$answer -> fields_failed = $fields_failed;
$answer -> status = "0";
$answer -> message = "Some data failed validation!";
}

print_r($answer);
exit;

Is it possible to prevent XSS and other security issues using this same approach, or, with 1 line "treat" all post data?