Add !!user_id!! to Paid Memberships Pro Emails

add-user-id-to-pmpro-email.php

<?php
/**
 * Add's !!user_id!! variable to all Paid Memberships Pro emails.
 * Add this code to your site by following this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_email_data_example( $data, $email ) {

    $user = get_user_by( "login", $data['user_login'] );

    $data['user_id'] = $user->ID; //adjust 'user_id' for the variable you want to use instead.

    return $data;
}
add_filter( "pmpro_email_data", "my_pmpro_email_data_example", 10, 2 );