your code to set the session:
<?php
if (!session_id()) session_start();
if($_SERVER["REQUEST_METHOD"] == "POST") {
$_SESSION["WADA_Update_mre"] = "".$row_WADAmre['autoNum'] ."";
}
?>
is at lines 11- 16. this is before the code for the WADAmre recordset which is at line 64 - 72.
the session must be set after the recordset, not before.