Only allow specific email addresses and usernames to check out using PMPro. Forked from Register Helper.

pmpro_allowlist.php

<?php

/*
 * Plugin Name: PMPro Allowlist
 * Plugin URI: https://www.paidmembershipspro.com
 * Description: Only allow specific email addresses and usernames to check out using PMPro. Forked from Register Helper.
 * Version: 1.0
 * Author: Paid Memberships Pro
 * Author URI: https://www.paidmembershipspro.com
 */

/**
 * Add settings to edit membership level page.
 */
function pmpro_allowlist_after_other_settings()
{
	$level = $_REQUEST['edit'];
	$restrict_emails = pmpro_getOption("level_" . $level . "_restrict_emails");
	?>
	<h3 class="topborder">Restrict by Email</h3>
	<p>To restrict signups to specific email addresses, enter those email addresses below, one per line. If blank, signups will not be restricted.</p>
	<textarea rows="10" cols="80" name="restrict_emails" id="restrict_emails"><?php echo str_replace("\"", "&quot;", stripslashes($restrict_emails))?></textarea>
	<?php

	$restrict_usernames = pmpro_getOption("level_" . $level . "_restrict_usernames");
	?>
	<h3 class="topborder">Restrict by Username</h3>
	<p>To restrict signups to specific users or usernames, enter those usernames below, one per line. If blank, signups will not be restricted.</p>
	<textarea rows="10" cols="80" name="restrict_usernames" id="restrict_usernames"><?php echo str_replace("\"", "&quot;", stripslashes($restrict_usernames))?></textarea>
	<?php
}
add_action("pmpro_membership_level_after_other_settings", "pmpro_allowlist_after_other_settings");

/**
 * Save membership level settings.
 */
function pmpro_allowlist_save_membership_level($saveid)
{
	$restrict_emails = $_REQUEST['restrict_emails'];
	pmpro_setOption("level_" . $saveid . "_restrict_emails", $restrict_emails);

	$restrict_emails = $_REQUEST['restrict_usernames'];
	pmpro_setOption("level_" . $saveid . "_restrict_usernames", $restrict_emails);
}
add_action("pmpro_save_membership_level", "pmpro_allowlist_save_membership_level");

/**
 * Enforce allowlist at checkout.
 */
function pmpro_allowlist_registration_checks($okay)
{
	global $current_user;

	//only check if we're okay so far and there is an email to check
	if($okay && (!empty($_REQUEST['bemail']) || !empty($current_user->user_email)))
	{
		//are we restricting emails for this level
		global $pmpro_level;
		$restrict_emails = pmpro_getOption("level_" . $pmpro_level->id . "_restrict_emails");
		if(!empty($restrict_emails))
		{
			$restrict_emails = strtolower(str_replace(array(";", ",", " "), "\n", $restrict_emails));
			if(!empty($current_user->user_email))
				$needle = strtolower($current_user->user_email);
			else
				$needle = strtolower($_REQUEST['bemail']);
			$haystack = explode("\n", $restrict_emails);
			array_walk( $haystack, function( &$val ) { 
				$val = trim($val);
				return $val;
			});
			if(!in_array($needle, $haystack))
			{
				global $pmpro_msg, $pmpro_msgt;
				$pmpro_msg = "This membership level is restricted to certain users only. Make sure you've entered your email address correctly.";
				$pmpro_msgt = "pmpro_error";
				$okay = false;

				//no further checks here
				return $okay;
			}
		}

		//are we restricting user names for this level
		$restrict_usernames = pmpro_getOption("level_" . $pmpro_level->id . "_restrict_usernames");

		if(!empty($restrict_usernames))
		{
			$restrict_usernames = strtolower(str_replace(array(";", ",", " "), "\n", $restrict_usernames));
			if(!empty($current_user->user_login))
				$needle = strtolower($current_user->user_login);
			else
				$needle = strtolower($_REQUEST['username']);
			$haystack = explode("\n", $restrict_usernames);
			array_walk( $haystack, function( &$val ) { 
				$val = trim($val);
				return $val;
			});
			if(!in_array($needle, $haystack))
			{
				global $pmpro_msg, $pmpro_msgt;
				$pmpro_msg = "This membership level is restricted to certain users only. Make sure you are logged into your existing account and using the proper username.";
				$pmpro_msgt = "pmpro_error";
				$okay = false;
			}
		}
	}

	return $okay;
}
add_filter("pmpro_registration_checks", "pmpro_allowlist_registration_checks");