Restrict Membership Signup by Email Domain (Useful for Education, Corporate, or Association Memberships)

my_pmpro_checkout_restrict_email_domain.php

<?php
function restrict_email($value)
{
	$email = $_REQUEST['bemail'];
		
	if(!check_validity($email))
	{
		global $pmpro_msg, $pmpro_msgt;
		$pmpro_msg = "Please enter a valid email address";
		$pmpro_msgt = "pmpro_error";
		$value = false;
	}
	
	return value;
}
add_filter('pmpro_registration_checks','restrict_email', 10, 1);

//Taken from: http://www.bitrepository.com/how-to-extract-domain-name-from-an-e-mail-address-string.html
function getDomainFromEmail($email)
{
    // Get the data after the @ sign
    $domain = substr(strrchr($email, "@"), 1);
 
    return $domain;
}

function check_validity($email)
{
	$domain = getDomainFromEmail($email);
	
	$valid_domains = array("yahoo.com", "*.gmail.com", "*.domain.uk");
	foreach($valid_domains as $valid_domain)
	{
		$components = explode(".", $valid_domain);
		$domain_to_check = explode(".", $domain);
		
		if($components[0] == "*" && sizeof($domain_to_check > 2))
		{
			if($components[1] == $domain_to_check[1] && $components[2] == $domain_to_check[2])
			{
				return true;
			}
		}
		
		else
		{
			if(!(strpos($valid_domain, $domain) === false))
				return true;
		}
	}
	
	return false;
}

I've forked this gist here: https://gist.github.com/ideadude/35dfe909d80b9926e8659973fe970c64

I can no longer edit gists created under the strangerstudios user and needed to fix a few things.

@laurenhagan0306 @ideadude, i propose to add:
if(is_null($email)){
return $value;
}
in line 11, because if the membership is renewed, $email is NULL. However the NULL check is done in the native pmpro filter.

I have used this but showing critical error in line number 37. would you pls check this...

thanks in advance