Get (part of) the query string.
The type parameter is either one of the HttpQueryString::TYPE_* constants or a type abbreviation like "b" for bool, "i" for int, "f" for float, "s" for string, "a" for array and "o" for a stdClass object.
keykey of the query string param to retrieve
typewhich variable type to enforce
defvaldefault value if key does not exist
deletewhether to remove the key/value pair from the query string