I got character issue

I can’t report my problem 

in

https://ww.wp.xz.cn/support/plugin/auto-post-thumbnail/

my problem is encoding problem 

same with this post.

https://ww.wp.xz.cn/support/topic/not-working-with-cyrillic-titles/

I couldn’t find where I should correct code 

$auto_image_post_title = mb_convert_encoding(get_the_title($post->ID), ‘HTML-ENTITIES’, ‘UTF-8’);

$auto_image_post_title = preg_replace(‘~^(&([a-zA-Z0-9]);)~’,htmlentities(‘${1}’),$auto_image_post_title);

add this code and update or let me know the name of PHP.

It bothers me all day