shortcode not return any thing in Gutnburg

There are 2 major bugs here

Problem 1: Your shortcode registration is invalid

You should be seeing lots of messages about this in your PHP error log

add_shortcode('splite', 'splite_article');

There is no function named splite_article, there’s a class function but the code didn’t tell it to use it. So instead of calling your shortcode function, it generates a PHP error message and puts it in the log.

add_shortcode expects a PHP callable value, so splite_article is equivalent to splite_article(), but you need $this->splite_article().

So instead use the appropriate callable [ $this, 'splite_article' ]

Problem 2: Shortcodes do not echo

echo $content;

That’s not how shortcodes work, shortcode callbacks do not echo HTML, they return it. This shortcode will be breaking a lot of things as a result of this.

Luckily the solution is simple, return the shortcodes content instead.