I would not add a new parameter to the function. I would create a new function `parseLayout` instead. To avoid duplicate code, I would move the content to a private method which is called by `parseMedia` and `parseLayout`. 
The reasons are:
* We are more flexible when we use an own function for layouts. What if we want to add a new parameter to it for some reason?
* Today the code may be similar, but in future it may be different which would result in funny code in this function.
* The function name doesn't match what it does anymore.
* Currently, the `$cid` parameter isn't used at all in the function and chances are high we will deprecate and remove it. We can't do that nicely if we add parameters behind it.