I am trying something basic but I can't seem to figure it out or I am not even sure if it is possible to be done in a child theme.

What is am trying is to organize the the codes in the functions.php file in the child theme by creating a separate directory for include files and have all the files in there.

Basically, here is the code in my functions.php file:

require_once( get_stylesheet_directory_uri() . '/inc/myfile.php');

And then myfile.php got this code:

function myfunction( $src ) {

add_filter( 'script_loader_src', 'myfunction');

But then I get this error:

PHP Fatal error:  Call to undefined function add_filter()

So now I am wondering if there is a way for me to do what I am trying to achieve in a child theme. I have tried this approach in a parent theme and it seemed to work fine.

Thanks in advance for explanation and suggestions.

1 Answer 1


What you're trying to do is possible.

When including php files, use get_stylesheet_directory() in child themes and get_template_directory() in parent themes.

E.g. require_once( get_stylesheet_directory() . '/inc/myfile.php');

get_stylesheet_directory_uri() and get_template_directory_uri() will return URLs. Those functions are useful when enqueuing public assets such as stylesheets and JavaScript.

Also, setting allow_url_include to Off in your php.ini will provide better error reporting in these situations (source).

  • Yes, what you suggested is what I have in my code, see codes in the post above. My problem is that in my file.php inside the inc directory, when I use the add_filter code, it throws the error that add_filter is an undefined function.
    – drifter
    Sep 4, 2016 at 13:30
  • No, our code is not the same! Mine works :) Take a closer look please. You are using get_stylesheet_directory_uri() and I'm using get_stylesheet_directory(). Those are two different functions. Here's a great supplement to the Codex on loading files within WordPress. Sep 4, 2016 at 14:54
  • Sorry, I missed that. Thanks a lot! My code works now. Thanks for the reference links as well. They helped a lot! :)
    – drifter
    Sep 4, 2016 at 17:07
  • No worries! Glad it's working now. Sep 4, 2016 at 17:13

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