lib/Tumblr/API/Client.php
public function unfollow($blogName)
    {
        $options = array('url' => $this->blogUrl($blogName));

        return $this->postRequest('v2/user/unfollow', $options, false);
    }
public function unfollow($blogName)
    {
        $options = array('url' => $this->blogUrl($blogName));

        return $this->postRequest('v2/user/unfollow', $options, false);
    }
Unfollow a blog

@param  string $blogName the name of the blog to follow
@return array  the response array