How to get_the_content with proper formatting inside functions.php?

To get the post or page content inside WordPress functions.php with all the HTML tags you need to use the_content filter.

This method of getting the content data is very helpful when creating custom REST API points or Plugins.

global $post;

$my_variable = apply_filters('the_content', get_post_field('post_content', $post->id));

TL;DR

You have probably landed here after browsing the WEB for “get_the_content() is not formated properly” or something similar. The reason is that get_the_content() is not passed
through the ‘the_content’ filter. Wich means that $my_variable = apply_filters(‘the_content’, get_the_content($post->id)); will work as well. The reason I’m using get_post_field(‘post_content’, $post->id) is because sometimes in get_the_content() and the_content()  functions a variable sent to a PHP count() could be NULL and that is an issue for PHP 7.2