I currently have a global function in my functions.php file

ein_error_log($message)
{
      //push out $message to file... 
}

But I want to start using it in my MU-Plugin directory and it doesn't know it exists. So I assume it's because MU-Plugins folder is read before the theme folder in WordPress's hierarchy, which makes sense.

But if the hierarchy is the case, how do I distinguish which MU-Plugin runs first to make sure all other MU-Plugin files can run dependent on said file?

I currently have a global function in my functions.php file

ein_error_log($message)
{
      //push out $message to file... 
}

But I want to start using it in my MU-Plugin directory and it doesn't know it exists. So I assume it's because MU-Plugins folder is read before the theme folder in WordPress's hierarchy, which makes sense.

But if the hierarchy is the case, how do I distinguish which MU-Plugin runs first to make sure all other MU-Plugin files can run dependent on said file?

-- UPDATE--

I have my ein_error_log($message) method transferred into an mu-plugin file. I realized how silly it was to have mu-plugin files dependent on a method inside function.php file. But I still wanted the other mu-plugin files to also use this error logging method. This requires some mu-plugins to have a dependency. Its small, but important to me.