Limit signups on a particular Membership by email domain

mepr-limit-signup-by-email-domain.php

<?php
function ends_with($haystack, $needle = '.ac.uk') {
  return (($temp = strlen($haystack) - strlen($needle)) >= 0 && strpos($haystack, $needle, $temp) !== FALSE);
}

function check_email_domain($errors) {
  $membership_id = 123; //Change this to reflect your Membership ID
  
  if($membership_id != $_POST['mepr_product_id']) {
    return $errors;
  }
  
  $email = stripslashes($_POST['user_email']);
  if(!ends_with($email)) {
    $errors[] = "Sorry, only valid .ac.uk email addresses are allowed on this Membership";
  }
  
  return $errors;
}
add_filter('mepr-validate-signup', 'check_email_domain');