This draws a rotated ellipse. If you don't want filled ellipses, then you don't need the triangle function.
function triangle($x1,$y1, $x2,$y2, $x3,$y3, $colour) {
global $im;
$coords = array($x1,$y1, $x2,$y2, $x3,$y3);
imagefilledpolygon($im, $coords, 3, $colour);
}
function rotatedellipse($cx, $cy, $width, $height, $rotateangle, $colour, $filled=true) {
global $im;
$step=15;
$cosangle=cos(deg2rad($rotateangle));
$sinangle=sin(deg2rad($rotateangle));
$squishratio = $height/$width;
$nopreviouspoint = true;
for ($angle=0; $angle<=(180+$step); $angle+=$step) {
$ox = ($width * cos(deg2rad($angle)));
$oy = ($width * sin(deg2rad($angle))) * $squishratio;
$x = ($ox * $cosangle) - ($oy * $sinangle);
$y = ($ox * $sinangle) + ($oy * $cosangle);
if ($nopreviouspoint) {
$px=$x;
$py=$y;
$nopreviouspoint=false;
}
if ($filled) {
triangle($cx, $cy, $cx+$px, $cy+$py, $cx+$x, $cy+$y, $colour);
triangle($cx, $cy, $cx-$px, $cy-$py, $cx-$x, $cy-$y, $colour);
} else {
imageline($im, $cx+$px, $cy+$py, $cx+$x, $cy+$y, $colour);
imageline($im, $cx-$px, $cy-$py, $cx-$x, $cy-$y, $colour);
}
$px=$x;
$py=$y;
}
}
