advanced tag cloud widget css classes

add_filter ( 'wp_tag_cloud', 'tag_cloud_widget_advanced_classes' );

function tag_cloud_widget_advanced_classes( $taglinks ) {
    $tags = explode('</a>', $taglinks);
    $regex1 = "#(.*tag-link[-])(.*)(' title.*)#e";
    $regex2 = "#(.*style='font-size:)(.*)((pt|px|em|pc|%);'.*)#e";
    $regex3 = "#(style='font-size:)(.*)((pt|px|em|pc|%);')#e";
    $regex4 = "#(.*class=')(.*)(' title.*)#e";
    foreach( $tags as $tag ) {
        $tag = preg_replace($regex1, "('$1$2 tag-slug-'.get_tag($2)->slug.'$3')", $tag ); //add .tag-slug-{slug} class
        $size = preg_replace($regex2, "(''.round($2).'')", $tag ); //get the rounded font size
        $tag = preg_replace($regex3, "('')", $tag ); //remove the inline font-size style
        $tag = preg_replace($regex4, "('$1tag-size-'.($size).' $2$3')", $tag ); //add .tag-size-{nr} class
        $tagn[] = $tag;
    }
    $taglinks = implode('</a>', $tagn);
return $taglinks;
}