Loading class files via autoload method

Question

We have core classes created for theme and we are moving those classes to client-mu-plugins. Is there any way we can load all of the classes without adding require_once function for every single files? I tried spl_autoload_register() function in every single ways but It's not loading.

File structure in plugin now

plugin_folder
  -inc
      - frontend
         -class-post.php
         -class-design.php
         -class-video.php
      - modules
         -class-query.php
         -class-config.php
      - queries
  - plugin-name.php

All of the class files also have Namespace defined. I'm not getting an idea on how to include those in custom plugins so it would work like it was working in theme folder. Could we use autoloader in someway? Appreciate your comments and help.

Namespace are defined on class files are like:

Foo\Frontend
Foo\Modules
Foo\Queries

Tried: https://github.com/tommcfarlin/simple-autoloader-for-wordpress/

Thanks

Answer 1

Placed in the theme (e.g. in functions.php), something like the below tweaked for your context might work.

I assumed you want to include all the .php files from specific directories but only for the specified plugins when they are active:

add_action('after_setup_theme', 'add_child_plugins');

function add_child_plugins() {
    $include_plugins = array('plugin1',); //plugin folder names
    //relevant folders inside those plugin, assuming consistent
    $include_subfolders = array('inc/frontend', 'inc/modules',);
    foreach ($include_plugins as $plugin) {
        $plugin_str = $plugin . '/' . $plugin . '.php';
        // asssume only need from activated plugins
        //if (is_plugin_active($plugin_str)) { uncomment for normal non mu-plugins
            foreach ($include_subfolders as $subfolder) {
                $path = WPMU_PLUGIN_DIR . "/$plugin/$subfolder/*.php";
                foreach (glob($path) as $file) {
                    include_once $file;
                }
            }
        //}uncomment for normal non mu-plugins
    }
}

I'm sure there are alternative more elegant or sophisticated ways :-)