Specifies the offset into the dash pattern to start the dash.
Background color
 
Stroke color
 
Fill color
 
Specifies the offset into the dash pattern to start the dash.
Parameters
dash_offsetfloatdash offset
function setStrokeDashOffset($strokeColor, $fillColor, $backgroundColor)
{
    $draw = new \ImagickDraw();

    $draw->setStrokeColor($strokeColor);
    $draw->setFillColor($fillColor);
    $draw->setStrokeWidth(4);
    $draw->setStrokeDashArray([20, 20]);
    $draw->setStrokeDashOffset(0);
    $draw->rectangle(100, 50, 225, 175);

    //Start the dash effect halfway through the solid portion
    $draw->setStrokeDashOffset(10);
    $draw->rectangle(275, 50, 400, 175);

    //Start the dash effect on the space portion
    $draw->setStrokeDashOffset(20);
    $draw->rectangle(100, 200, 225, 350);
    $draw->setStrokeDashOffset(5);
    $draw->rectangle(275, 200, 400, 350);

    $image = new \Imagick();
    $image->newImage(500, 400, $backgroundColor);
    $image->setImageFormat("png");
    $image->drawImage($draw);

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