imageField - how to read coordinates???

[double-f]

the problem:
i cannot read the coordinates generated by a click on the image_field in the form.
using get method, the part of the url shows:
?ch.x=100&ch.y=150
that's the way the browser sends it to the server, with the fxxxxng 'dot' between

i try to read it using different methods in php:

1. $x = $ch.x;
   (bullshit, because the 'dot' inbetween makes a concatenation operation)
   -----
2. $x=$HTTP_GET_VARS['ch.x']
   (does not work... ? keys cannot be named with the 'dot' ?)
   ----
3. another way is to generate hidden fields with names without 'dot' and passing the coordinates to them (in javascript). It could be possible using onClick event and javascript submit() function, but i do not know how to read the 'clicked' coordinates in javascript to make a proper assigment.
   ----
4. in perl it is possible to get the whole query_string, do some manipulations, but in PHP i could not find this kind of function (look at point 2 - i just figured it out that way - does not work)

help! anyone?

[double-f]

ok, the 4th method worked out, maybe lame but works:

$qs = getenv('QUERY_STRING');
$fx_str = substr($qs, (strpos($qs, 'ch.x=')+5));
$temp_x = strpos($fx_str, '&');
if ($temp_x != 0) {
$fx_str = substr($fx_str, 0, $temp_x);
}
$fy_str = substr($qs, (strpos($qs, 'ch.y=')+5));
$temp_y = strpos($fy_str, '&');
if ($temp_y != 0) {
$fy_str = substr($fy_str, 0, $temp_y);
}