check_availability.php

<?php
include('../includes/db.php');

$car_id = intval($_GET['car_id']);
$start = $_GET['start'];
$end = $_GET['end'];

// 1. Get total quantity from cars table
$carQ = mysqli_query($conn, "SELECT quantity FROM cars WHERE car_id=$car_id");
$car = mysqli_fetch_assoc($carQ);
$total_quantity = $car['quantity'];

// 2. Count overlapping bookings
$check = mysqli_query($conn, "
    SELECT COUNT(*) as booked_count 
    FROM bookings 
    WHERE car_id=$car_id 
      AND status IN ('Pending Payment','Awaiting Approval','Approved')
      AND start_date <= '$end' 
      AND end_date >= '$start'
");
$booked = mysqli_fetch_assoc($check);

// 3. Remaining available cars
$available = $total_quantity - $booked['booked_count'];
if ($available < 0) $available = 0;

header('Content-Type: application/json');
echo json_encode(['available' => $available]);