The null coalescing operator (??) has been added as syntactic sugar for the common case of needing to use a ternary in conjunction with isset().
It returns its first operand if it exists and is not NULL; otherwise it returns its second operand.
Coalesce returns the first none null argument from a set of arguments.
Only the first non null argument is return, all subsequent arguments are ignored.
The function will evaluate to null if all arguments are null.
