Building a Shortcode for Lorempixel

LoremPixel shortcode

// http://lorempixel.com/ 
// [phpic width="300" height="200"]

<?php
function grab_random_picture($atts){
	extract(shortcode_atts(array(
		'width' => 400,
		'height' => 300,
	), $atts));
	return '<img src="http://lorempixel.com/'. $width . '/' . $height . '" />';
}
add_shortcode('phpic', 'grab_random_picture');