Example

function setStrokeLineCap($strokeColor, $fillColor, $backgroundColor)
{
    $draw = new \ImagickDraw();
    $draw->setStrokeColor($strokeColor);
    $draw->setFillColor($fillColor);
    $draw->setStrokeWidth(25);

    $lineTypes = [\Imagick::LINECAP_BUTT, \Imagick::LINECAP_ROUND, \Imagick::LINECAP_SQUARE,];

    $offset = 0;

    foreach ($lineTypes as $lineType) {
        $draw->setStrokeLineCap($lineType);
        $draw->line(50 + $offset, 50, 50 + $offset, 250);
        $offset += 50;
    }

    $imagick = new \Imagick();
    $imagick->newImage(300, 300, $backgroundColor);
    $imagick->setImageFormat("png");
    $imagick->drawImage($draw);

    header("Content-Type: image/png");
    echo $imagick->getImageBlob();
}