src/CarteBlanche/Library/Callback.php
protected function _executeCallbackAsReference($fct, &$entry_value)
    {
        list($fct_name, $args) = $this->_parseCallbackFunctionName($fct);
        array_unshift($args, $entry_value);
        $entry_value = $this->_executeCallback($fct_name, $args);
        return $entry_value;
    }
protected function _executeCallbackAsReference($fct, &$entry_value)
    {
        list($fct_name, $args) = $this->_parseCallbackFunctionName($fct);
        array_unshift($args, $entry_value);
        $entry_value = $this->_executeCallback($fct_name, $args);
        return $entry_value;
    }
Execution of one callback on a value returning it by reference

@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, passed by reference
@return  mixed