update_currency_per_level.php

/*
	Change currencies depending on Paid Memberships Pro level. 
	Add this code to your active theme's functions.php or a custom plugin. 
	This is just an example that will need to be tweaked for your needs.
	
	Other places to look into swapping currencies:
	* Levels page.
	* Invoices page.
	* In emails.
	* In membership levels table in admin.
	* When using discount codes.
*/

/*
	Global to store levels with non-default currencies
	Keys are level ids. Values are an asrray with the currency abbreviation and symbol as the first and second entries. 
*/
global $level_currencies;
$level_currencies = array(
		5 => array("EUR", "€"),
		6 => array("GBP", "£")
	);

//main function to check for a currency level and update currencies
function update_currency_per_level($level_id)
{
	global $pmpro_currency, $pmpro_currency_symbol, $level_currencies;

	foreach($level_currencies as $level_currency_id => $level_currency)
	{
		if($level_id == $level_currency_id)
		{
			$pmpro_currency = $level_currency[0];
			$pmpro_currency_symbol = $level_currency[1];
		}
	}
}

//change currency on checkout page
function my_pmpro_checkout_level($level)
{
	update_currency_per_level($level->id);

	return $level;
}
add_filter("pmpro_checkout_level", "my_pmpro_checkout_level");

//change currency when sent as a request param
function my_init_currency_check()
{
	if(!empty($_REQUEST['level']))
		return update_currency_per_level(intval($_REQUEST['level']));
}
add_action("init", "my_init_currency_check");

//params in the admin
function my_admin_init_currency_check()
{
	if(!empty($_REQUEST['edit']) && !empty($_REQUEST['page']) && $_REQUEST['page'] == 'pmpro-membershiplevels')
		return update_currency_per_level(intval($_REQUEST['edit']));
}
add_action("admin_init", "my_admin_init_currency_check");