Set minimum length for username checkouts for Paid Memberships Pro

pmpro_check_username_length.php

<?php

function pmpro_check_username_length( $pmpro_continue_registration ) {
	
	//only bother if things are okay so far

	if(!$pmpro_continue_registration)
		return $pmpro_continue_registration;
	
	$username = $_REQUEST['username'];
	if ( !is_user_logged_in() ) {
	if ( strlen( $username ) < 5 ) {
		pmpro_setMessage( esc_html__( 'Your username must be at least 5 characters long.' ), 'pmpro_error' );
		return false;
	}
	}
	
	return $pmpro_continue_registration;
	}


add_filter( 'pmpro_registration_checks', 'pmpro_check_username_length' );