src/CarteBlanche/Library/Callback.php
protected function _executeCallbackAsBoolean($fct, $entry_value)
    {
        list($fct_name, $args) = $this->_parseCallbackFunctionName($fct);
        array_unshift($args, $entry_value);
        $response = $this->_executeCallback($fct_name, $args);
        if ($response==$entry_value)
            return true;
        return (bool) $response;
    }
protected function _executeCallbackAsBoolean($fct, $entry_value)
    {
        list($fct_name, $args) = $this->_parseCallbackFunctionName($fct);
        array_unshift($args, $entry_value);
        $response = $this->_executeCallback($fct_name, $args);
        if ($response==$entry_value)
            return true;
        return (bool) $response;
    }
Execution of one callback on a value

@param   string  $fct            The function name to execute, it will be called passing the current value as first argument
@param   mixed   $entry_value    The entry value to execute the callback
@return  bool