code/LivePubHelper.php
public static function eval_php($code)
    {
        if (self::is_publishing()) {
            return self::$context=='html'
                ? '<?php echo eval(\'' . addcslashes($code, "'") . '\'); ?>'
                : 'eval(\'' . addcslashes($code, "'") . '\')';
        } else {
            return eval($code);
        }
    }
public static function eval_php($code)
    {
        if (self::is_publishing()) {
            return self::$context=='html'
                ? '<?php echo eval(\'' . addcslashes($code, "'") . '\'); ?>'
                : 'eval(\'' . addcslashes($code, "'") . '\')';
        } else {
            return eval($code);
        }
    }
evaluates the given php code unless we're currently publishing, in which case it
returns php code that will echo the return value of the eval'd code.

@param string $code
@return string