form helper callback is not working

[eluser]johnmerlino[/eluser]
Hey all,

In this code:

Code:

// in views/partials/_contact.php
        echo contact_formatter('Your Name:','Add your name',"form_input()",'username');

// in helpers/layout_helper.php

    function contact_formatter($label,$text,$callback = null,$callback_arg){
        $str_builder = '';
        $str_builder .= "<div class='rowElem'>";
        $str_builder .= "<label>{$label}<span class='small'>{$text}</span></label>";
        $str_builder .= call_user_func($callback,$callback_arg); //(is_callable($callback)) ?
        $str_builder .= "</div>";
        return $str_builder;
    }

I get a php error:

Code:

Message: call_user_func() expects parameter 1 to be a valid callback, function 'form_input()' not found or invalid function name

thanks for response