<?php
// create a blank image
$image = imagecreatetruecolor(400, 300);
// fill the background color
$bg = imagecolorallocate($image, 0, 0, 0);
// choose a color for the ellipse
$col_ellipse = imagecolorallocate($image, 255, 255, 255);
// draw the white ellipse
imagefilledellipse($image, 200, 150, 300, 200, $col_ellipse);
// output the picture
header("Content-type: image/png");
imagepng($image);
?>
The above example will output
something similar to: