1. Go to this page and download the library: Download humanmade/mercator-redirect library. Choose the download type require.
2. Extract the ZIP file and open the index.php.
3. Add this code to the index.php.
<?php
require_once('vendor/autoload.php');
/* Start to develop here. Best regards https://php-download.com/ */
humanmade / mercator-redirect example snippets
// Default mu-plugins directory if you haven't set it
defined( 'WPMU_PLUGIN_DIR' ) or define( 'WPMU_PLUGIN_DIR', WP_CONTENT_DIR . '/mu-plugins' );