Code:
echo "<img src='" . $imgstr . "' alt='description' />";
a little off-topic, but i wouldn't recommend using alt if you want 'description' to show up on mouseovers. use title instead, since that will show the text on mouseovers in all modern browsers. (alt won't respond to mouseovers in mozilla browsers and firefox.) the alt attribute is used when the image doesn't load (or using lynx) and text is put in its place. really, i guess, you would want to use both attributes.
the only reason i mention this is that i find a lot of people using alt for mouseover text.