Manipulates the resultant url by adding this key value pair.
Declaration Syntax
Parameters
Remarks
This method will NOT overwrite any of the original parameters with
the same key or any other parameter that got added by this same
method previously with the same key. In addition, it is assumed
that is decoded and will encode the value as
x-www-form-urlencoded on output. Values that are null or equal
to "" will be skipped so that this method can be blindly called
without having to check if the value is present.