Wordpress admin notice always showing same message - php

Question

On the admin dashboard, I display admin notice to display the result of changes. I have production site and staging site. On the staging site, it works well. If I made changes, it's displaying the notice of appropriate message. But on production, it's same code as staging site. When I made changes, it's displaying the "cached" notice but not the appropriate message.
Here is my approach to solve this.
$flash_messages = maybe_unserialize(get_option('wp_flash_messages', array()));
print_r(flash_messages); exit;
This displays the 'cached' message.
delete_option('wp_flash_messages');
$flash_messages = maybe_unserialize(get_option('wp_flash_messages', array()));
print_r($flash_messages); exit;
I added delete_option() before get the message. But it returns the 'cached' message again.
EDIT : I cleared server cache as well.
It's really annoyed.
Can anyone help me?

Answer 1

Finally I found the issue is because of get_option() function is cached.
https://developer.wordpress.org/reference/functions/get_option/#source
Here you can see the function get cached data first and if not, look through db and get option.
ANSWER
wp_cache_flush();
This resolved the problem.

Answer 2

1) You can delete cacle from WPEngine is a managed WordPress hosting provider. They run their own caching solution, so their customers don’t need to install a caching plugin.
If you are unable to notice changes take effect immediately, then you can easily clear WPEngine cache from your WordPress admin area.
2) You can also delete cache by using wp super cache plugin