This function iterates over the HTTP variables included within a request. Calling it with NULL causes it to return the name
of the first variable. Subsequent variables are retrieved by passing the function the name of the previous variable. This
function returns NULL when called with the name of the final variable or when not called from a web service.
Calling this function repeatedly returns all the variables exactly once, but not necessarily in the order they appear in the
HTTP request. The variables url or url1, url2, ..., url10 are included if URL PATH is set to ON or ELEMENTS, respectively.
When used within a stored procedure that is called by an HTTP web service, the following example returns the name of the first
DECLARE variable_name LONG VARCHAR;
DECLARE variable_value LONG VARCHAR;
SET variable_name = NULL;
SET variable_name = NEXT_HTTP_VARIABLE( variable_name );
SET variable_value = HTTP_VARIABLE( variable_name );