Seems like you could build your query according to what it entered. I take it you are having trouble because field 7 might be blank and you don't want to search for a blank field 7, you want to ignore field 7?

So just do a:
if ($_POST["gender"]) $qry.="gender='". $_POST["gender"]."',";
for each field.

Note the .= which keeps adding each part to the query.

Then trim the last comma off and use $qry as your query.

Good luck