<?php
// ... (lines 1-464)
    if ($action === 'get_payment_details') {
        header('Content-Type: application/json');
        $payment_id = (int)$_GET['payment_id'];
        $stmt = db()->prepare("SELECT p.*, i.customer_id, c.name as customer_name, o.name as outlet_name 
                               FROM payments p 
                               JOIN invoices i ON p.invoice_id = i.id 
                               JOIN customers c ON i.customer_id = c.id 
                               LEFT JOIN outlets o ON i.outlet_id = o.id
                               WHERE p.id = ?");
        $stmt->execute([$payment_id]);
        echo json_encode($stmt->fetch(PDO::FETCH_ASSOC));
        exit;
    }
// ...