PhP是/否和切换/案例例程的问题

I have taken over a PhP application that populates events in a MySQL database.

I have modified it so it allows events to have multiple recipients. No issues.

My issue is that when a multi user event is clicked on to update or more importantly to delete I ask using a Javascript function 'Apply to all users on this event?'. Question works fine. I appreciate PhP is server side and JS runs on the client side.

So what I tried is a hidden field in my edit form which defaults to 'adddetails' and if they press yes to the multi user question populate it with addmultidetails (which I verified by making a text field temporarily). You can see from the original <form> tage that adddetails is hard coded into the post url as a GET paramter.

<form action="data.php?method=adddetails<?php echo isset($event)?"&id=".$event->Id:""; ?>"
      class="fform" id="fmit" name="fm" method="post">

// data.php //

<?php

session_start(); 

function add($st, $et, $sub, $ade){
  return $ret;
}

function addDetailed($st, $et, $sub, $ade, $dscr, $loc, $color, $tz){
   return $ret;
}

function listByRange($sd, $ed){
  return $ret;
}

function list($day, $type){
}

function update($id, $st, $et){  
   return $ret;
}

function updateDetailed($id, $st, $et, $sub, $ade, $dscr, $loc, $color, $tz){ 
  return $ret;
}

function updateMultiDetailed($id, $st, $et, $sub, $ade, $dscr, $loc, $color, $tz){ 
   return $ret;
}

function remove($id){
  return $ret;
}

$method = $_GET["method"];
switch ($method) {
    case "add":
        break;
    case "list":
        break;
    case "update":
        break; 
    case "remove":
        break;
    case "adddetails":
        break;
    case "addmultidetails":
        break; 
}
echo json_encode($ret); 

?>

All the post data as originally posted is correct, however if I try to access the hidden field, updmethod, and changed the data.php to have $method = $_POST["updmethod"]; my program just freezes without any error messages (I have error_reporting(E_ALL); in my modules).

Then I tried another form to store the hidden updmethod so I could just change the method= in

<form action="data.php?method=adddetails<?php echo isset($event)?"&id=".$event->Id:""; ?>"
      class="fform" id="fm" name="fm" method="post">

to be built dynamically but am having no success there either.

I would appreciate any help with this. I am not being lazy. I have spent 2 days working on a problem I thought I could resolve quickly and have read 'tutorials' on Server side/Client side relationship. Tried to understand Ajax etc but no matter what I seem to achieve I then encounter another wall.

I know my problem all stems from the Php/Javascript realtionship and trying to get the response from the Javascript function to my Php....but I am stumped.

I will not be offended if I am told my approach is all wrong, but rememeber I am working with an existing code.