To do filled arcs, try something like this:
<?php
$diameter = 50;
imagearc($image, 25, 25, $diameter, $diameter, $start, $end, $color);
while($diameter > 0) {
imagearc($image, 25, 25, $diameter, $diameter, $start, $start + 1, $color);
imagearc($image, 25, 25, $diameter, $diameter, $end - 1, $end, $color);
$diameter--;
}
?>
...well you get the point. It's a kludge, and *very* slow, but it's free.