I wrote a simple function that can draws an arc counter-clockwisekly. Here it is :
<?php
function imagearcCC(&$im, $cx, $cy, $w, $h, $s, $e, $c) {
$start = 360 - $e;
$end = 360 - $s;
return imagearc($im, $cx, $cy, $w, $h, $start, $end, $c);
}
?>
The params of this function is exactly the same as the usual imagearc function.