Thank you for the thoughts, unset did not work on the HTTP_POST_VARS array.
I am creating a large number of variables on the fly by tagging a number onto the end and posting them back to the same script, I am then accessing them by the $$ notation, however in a certain circumstance I check if something is set and then I do not want all these variables to be set - thus the wish to get rid of the post_vars_array.
I may be going about this the wroung way,
thank you for your help.