how to read imageField coordinates?

the problem:
i cannot read the coordinates generated by a click on the image_field.

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

i try to read it in different way in php:

$x = $ch.x;
(bullshit, because the 'dot' inbetween makes a concatenation operation)
-----
$x=$HTTP_GET_VARS['ch.x']
(does not work... ? keys cannot be named with the 'dot' ?)
----
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.

help! anyone?

php converts the dots to the underscore char "_".

so ?ch.x=100&ch.y=150
would be available in php as $ch_x & $ch_y.

###################

<BODY>

<?
echo $test_x,"<BR>\n";
echo $test_y,"<BR>\n";
?>

</BODY>