WordPressで絶対パスを相対パスに自動で置き換える

class relative_URI {
    public function __construct() {
        add_action('get_header', array(&$this, 'get_header'), 1);
        add_action('wp_footer', array(&$this, 'wp_footer'), 99999);
    }
    protected function replace_relative_URI($content) {
        $home_url = trailingslashit(get_home_url('/'));
        $top_url = preg_replace( '/^(https?:\/\/.+?)\/(.*)$/', '$1', $home_url );
        return str_replace( $top_url, '', $content );
    }
    public function get_header(){
        ob_start(array(&$this, 'replace_relative_URI'));
    }
    public function wp_footer(){
        ob_end_flush();
    }
}
$relative_URI = new relative_URI();