I am modifying a WordPress theme using a child theme. In my child theme folder, I have created a folder called “includes” (just like the parent) and have made edits to the content-post.php, content-single.php and content-single-portfolio.php files. I have added to the functions.php file in the child folder:
require_once( get_stylesheet_directory() . 'includes/content-post.php' );
require_once( get_stylesheet_directory() . 'includes/content-single.php' );
require_once( get_stylesheet_directory() . 'includes/content-single-portfolio.php' );
This causes a 500 internal error and I’m not sure why.
Reference:
http://codex.wordpress.org/Child_Themes
I also tried this solution and get the same 500 error:
WordPress Child Theme including includes files
your code probably converted to absolute url like
/home/user/public_html/wp-content/themes/my_themeincludes/content-single-portfolio.php
get_stylesheet_directory() should always be followed by forward slash
require_once( get_stylesheet_directory() . '/includes/content-post.php' );
Your best option is to check the error log, Most 500 error message are related to php timeout, specially if the site was previously working fine before you did any php modification.
You can also try doing something like this one by one for each file