EventEspresso Invoice Style

EventEspressoInvoiceStyle.php

<?php
namespace Academy\Core\Hooks\Filters;

use Academy\Core\Hooks\Filters;

class EventEspressoInvoiceStyle extends Filters
{
    public function __construct()
    {
        parent::__construct('FHEE__EE_Messages_Template_Pack__get_variation', 10, 8);
    }

    public function callback($cssFile)
    {
        $newCss = get_stylesheet_directory_uri().'/assets/css/'.strtolower(PLUGIN_PREFIX).'_invoices.css';

        return $newCss;
    }
}

Filters.php

<?php
namespace Academy\Core\Hooks;

class Filters
{
    private $hookName = '';

    public function __construct($hookName)
    {
        $this->hookName = $hookName;

        $this->register();
    }
  
    public function register()
    {
        add_filter($this->hookName, [$this, 'callback'], 10, 3);
    }
}