Alternative rounded corners

<?php
$cmd = " thumbnail.gif \( +clone -alpha extract ".
" \( -size 15x15 xc:black -draw 'fill white circle 15,15 15,0' -write mpr:arc +delete \) ".
" \( mpr:arc \) -gravity northwest -composite ".
" \( mpr:arc -flip \) -gravity southwest -composite ".
" \( mpr:arc -flop \) -gravity northeast -composite ".
" \( mpr:arc -rotate 180 \) -gravity southeast -composite \) ".
" -alpha off -compose CopyOpacity -composite ";

exec("convert $cmd rounded_corners.png");
?>