mypmpro-change-initial-amount-for-existing-members.php

<?php //do not copy
/**
 * This recipe will set the initial amount to the billing amount for a level
 * that the current logged in user has held a level of before.
 * 
 * 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/
 */

function my_pmpro_change_initial_amount_existing_members( $level ) {

	if( ! is_user_logged_in() ) {
		return $level;
	}
	
	global $current_user, $wpdb;

	
	$sqlQuery = "SELECT id FROM $wpdb->pmpro_membership_orders WHERE user_id = '" . esc_sql($current_user->ID) . "' AND membership_id = '".esc_sql( $level->ID )."' AND status NOT IN('refunded', 'review', 'token', 'error') LIMIT 1";

	$old_order_id = $wpdb->get_var($sqlQuery);
		
	if( ! empty( $old_order_id ) && ! empty( (float)$level->billing_amount ) ) {
		$level->initial_payment = $level->billing_amount;
	}
		
	return $level;
}
add_filter( 'pmpro_checkout_level', 'my_pmpro_change_initial_amount_existing_members', 10, 1 );