I'm creating a plugin I would like to use from other different plugins. This plugin declares classes and functions. So, I am thinking about the best way to include, from one plugin, a php file present in another plugin.

I think this should work:

require_once WP_PLUGIN_DIR . "/the-other-plugin/required-file.php";

But I am not sure; is it a good solution? I think this would work even if the-other-plugin is not enabled, and probably that is not a good idea.

This can be done also by using Must Use Plugins. Is this a best practice, or is the other solution better?

  • Why do you need to do this? and what is this other plugin your are borrowing functions from?
    – vancoder
    Commented Apr 25, 2013 at 16:38
  • If your plugin is installed as 'must use' in a multi-site installation then that constant is WPMU_PLUGIN_DIR.
    – alexg
    Commented Dec 29, 2015 at 17:40

1 Answer 1


In your plugin add a custom action to let other plugins start after your basic code has done the work:

// load basic classes
do_action( 'my_library_loaded', plugin_dir_path( __FILE__ ) );

Other plugins can start their work now like this:

add_action( 'my_library_loaded', 'other_plugin_init_handler' );

They will never do anything if your base plugin is not active.

The other plugin’s start function gets the correct path now as parameter:

function other_plugin_init_handler( $base_path )
    require_once $base_path . 'classes/Template_Handler.php' );

    $template = new Template_Handler;

You could also offer a custom class load function in the base plugin. The basic idea here is: Do not let other plugins guess a path.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.