checking id's to create or append tables

[rpjd]

I am submitting $_POST data to a results page.  The data comprises of references and text.  Each reference has its own table on the results page.  I need to check if an any of the table id's on the results page are the same as any of the references in $_POST, if any are, I am appending to the table, if not I am creatig a new table for the reference.  How do I check if a table id exists in order to append, then create tables for those that don't  Any help/guidance appreciated.