<?php
/**
 * Please note that if you use a stroke. ( Imagick::setStrokeWidth( 2 ) ) the
 * stroke is drawn outside the ellipse dimensions. 
 *
 * @param float $ox - Offset X, distance from the center of the ellipse till the left border of the image
 * @param float $oy - Offset Y, distance from the center of the ellipse till the top of the image
 * @param float $rx - X radius
 * @param float $ry - Y radius
 * @param float float $start - Starting angle in degrees.
 * @param float float $end - End angle in degrees.
 *
 */
ImagickDraw::ellipse( float $ox  , float $oy  , float $rx  , float $ry  , float $start  , float $end  );
?>

Example of drawing a full ellipse (from 0, 360) and outputting it as a PNG.
Do note, that this is  by default anti-aliased unlike the GD functions which only support it on lines that aren't on a transparent background.
<?php
$width =  200;
$height = 100;
$border = 2;

$img = new Imagick();
$img->newImage( $width, $height, new ImagickPixel( 'transparent' ) );

$draw = new ImagickDraw();
$draw->setStrokeColor( new ImagickPixel( 'black' ) );
$draw->setStrokeWidth( 2 );
$draw->setFillColor( new ImagickPixel( 'transparent' ) );
//Substract the border from the radius so it doesn't fall outside the screen.
$draw->ellipse( $width/2, $height/2, ($width/2)-$border, ($height/2)-$border, 0, 360 );
$img->drawImage( $draw );
$img->setImageFormat( "png" );

header( "Content-Type: image/png" );
echo $img;
?>