Increase memory and execution time for WP admins only.

my_init_memory.php

/*
	Increase memory and execution time for WP admins
	
	You can add code to your php.ini, .htaccess, or wp-config.php
	to increase execution times and memory limits to get WordPress
	and PMPro to work when it needs more memory, time, or both.
	
	However, sometimes you only need the extra memory and time
	when doing something an admin would be doing... like exporting
	a members list or orders table.
	
	If this is the case, you can use this code to selectively
	increase the execution time and memory for admins only.
	This will make sure that normal visitors don't end up
	using more memory or apache/etc services than they need to,
	which should make your site run smoother.
*/
function my_init_memory()
{
	if(current_user_can("manage_options") || current_user_can("pmpro_memberslistcsv") || current_user_can("pmpro_orderscsv"))
	{
		ini_set('max_execution_time', 300); //300 seconds = 5 minutes
		ini_set('memory_limit', '256M');
	}
}
add_action('init', 'my_init_memory', 1);

This recipe is included in the blog post on "Resolving Memory Issues When Exporting the Members List or Orders to CSV" at Paid Memberships Pro here: https://www.paidmembershipspro.com/resolving-memory-issues-when-exporting-the-members-list-or-orders-to-csv/