<?php
/* Read the image into the object */
$im = new Imagick( 'a.png' );
$im->setImageFormat("png");

/* Make the image a little smaller, maintain aspect ratio */
$im->thumbnailImage( 200, null );

/* Clone the current object */
$shadow = $im->clone();

/* Set image background color to black
        (this is the color of the shadow) */
$shadow->setImageBackgroundColor( new ImagickPixel( 'black' ) );

/* Create the shadow */
$shadow->shadowImage( 80, 3, 5, 5 );

/* Imagick::shadowImage only creates the shadow.
        That is why the original image is composited over it */
$shadow->compositeImage( $im, Imagick::COMPOSITE_OVER, 0, 0 );

/* Display the image */
header( "Content-Type: image/png" );
echo $shadow;