Only allow for the countries in the $restricted_countries array

pmpro-restrict-countries.php

<?php
/**
 * Only sell to specific countries by adding in the 'allowed' countries' in 
 * the $restricted_countries array.
 * change messages on line 35 and 51 for your site.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 * Country Codes - https://www.iban.com/country-codes
 */
function my_init()
{
	global $restricted_countries;
	
	//Only allow for the countries in the $restricted_countries array
	$restricted_countries = array(
					 1 => array('GB'), // Number is the level, then Add Country Codes, as many as true
					// 2 => array('US'), // copy for each level
	);
}

add_action('init', 'my_init');

function my_pmpro_registration_checks($value)
{
	global $restricted_countries, $pmpro_msg, $pmpro_msgt;
	
	$country = $_REQUEST['bcountry'];
	$level_id = $_REQUEST['level'];
	
	//only check if the level has restrictions
	if(array_key_exists($level_id, $restricted_countries) != in_array($country, $restricted_countries[$level_id]))
	{
		$pmpro_msg = "You must be a resident of Great Britain to register.";
		$pmpro_msgt = "pmpro_error";
			
		$value = false;
	}
	
	return $value;
}
add_filter("pmpro_registration_checks", "my_pmpro_registration_checks");

function my_pmpro_level_expiration_text($text, $level)
{
	global $restricted_countries, $pmpro_countries;
	
	if(array_key_exists($level->id, $restricted_countries ))
	{
		$text = $text." Only people from Great Britain can sign up here! ";
		
		//code for commas
		$i = 1;
		foreach($restricted_countries[$level->id] as $country)
		{
			$text = $text. $pmpro_countries[$country];
			
			if($i != count($restricted_countries[$level->id]))
				   $text = $text. ", ";
		
			$i++;
		}
		
	}
	
	return $text;
}
add_filter("pmpro_level_expiration_text", "my_pmpro_level_expiration_text", 10, 2);