PHP PHP array → JSON → MySQL row — same data, three formats

// PHP Array (how your PHP code stores it)
$customer = [
    'id'        => 5,
    'name'      => 'John Smith',
    'email'     => 'john@example.com',
    'plan_id'   => 2,
    'status'    => 'active'
];

// JSON (how the API sends it to Android/React/any client)
// json_encode() converts a PHP array to JSON automatically
{
    "id": 5,
    "name": "John Smith",
    "email": "john@example.com",
    "plan_id": 2,
    "status": "active"
}

// MySQL Row (how it's stored in the database)
// SELECT id, name, email, plan_id, status FROM customers WHERE id = 5;
// Returns: 5 | John Smith | john@example.com | 2 | active

// The magic: mysqli_fetch_assoc() returns a PHP array from MySQL,
// then json_encode() turns that array into JSON.
// That's all your API needs to do for a GET request.

Folder Structure Add these files to your existing PHP project

your-project-folder/
├── index.php              (your existing main file — unchanged)
├── config/
│   └── dbconnection.php   (your existing database connection — unchanged)
├── api/                   ← NEW folder
│   ├── config.php         ← NEW: CORS headers and shared functions
│   └── customers.php      ← NEW: the main API file for customer endpoints

PHP api/config.php — CORS headers + database connection

<?php
// ─────────────────────────────────────────────────────
// CORS Headers — allow any client to call this API
// For production: change * to your specific domain
// ─────────────────────────────────────────────────────
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
header("Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS");
header("Access-Control-Allow-Headers: Content-Type, Authorization");

// Handle browser preflight OPTIONS requests
if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    http_response_code(200);
    exit();
}

// ─────────────────────────────────────────────────────
// Database Connection
// Update these values to match your XAMPP setup
// ─────────────────────────────────────────────────────
$host   = 'localhost';
$dbname = 'isp_db';    // Your database name from phpMyAdmin
$user   = 'root';
$pass   = '';           // Blank by default on XAMPP

$conn = mysqli_connect($host, $user, $pass, $dbname);

if (mysqli_connect_errno()) {
    http_response_code(500);
    echo json_encode([
        'success' => false,
        'message' => 'Database connection failed: ' . mysqli_connect_error()
    ]);
    exit();
}
?>

PHP api/customers.php — Complete REST API (all 5 endpoints)

<?php
// Include CORS headers and database connection
require_once 'config.php';

// Get the HTTP method and optional customer ID from the URL
// Example: GET /api/customers.php?id=5
$method = $_SERVER['REQUEST_METHOD'];
$id     = isset($_GET['id']) ? (int)$_GET['id'] : null;

// Route requests to the correct handler based on method and ID
switch ($method) {
    case 'GET':
        $id ? getCustomer($conn, $id) : getAllCustomers($conn);
        break;
    case 'POST':
        createCustomer($conn);
        break;
    case 'PUT':
        $id ? updateCustomer($conn, $id) : errorResponse(400, 'Customer ID required for update');
        break;
    case 'DELETE':
        $id ? deleteCustomer($conn, $id) : errorResponse(400, 'Customer ID required for delete');
        break;
    default:
        errorResponse(405, 'Method not allowed');
}

// ─────────────────────────────────────────────
// GET all customers
// Endpoint: GET /api/customers.php
// ─────────────────────────────────────────────
function getAllCustomers($conn) {
    $query  = "SELECT c.id, c.name, c.email, c.phone, c.status,
                      p.plan_name, p.price
               FROM customers c
               LEFT JOIN internet_plans p ON c.plan_id = p.id
               WHERE c.status = 'active'
               ORDER BY c.name ASC";
    $result = mysqli_query($conn, $query);
    $customers = [];
    while ($row = mysqli_fetch_assoc($result)) {
        $customers[] = $row;
    }
    http_response_code(200);
    echo json_encode($customers);
}

// ─────────────────────────────────────────────
// GET one customer by ID
// Endpoint: GET /api/customers.php?id=5
// ─────────────────────────────────────────────
function getCustomer($conn, $id) {
    $stmt = mysqli_prepare($conn,
        "SELECT c.*, p.plan_name, p.price
         FROM customers c
         LEFT JOIN internet_plans p ON c.plan_id = p.id
         WHERE c.id = ?");
    mysqli_stmt_bind_param($stmt, 'i', $id);
    mysqli_stmt_execute($stmt);
    $result   = mysqli_stmt_get_result($stmt);
    $customer = mysqli_fetch_assoc($result);
    if ($customer) {
        http_response_code(200);
        echo json_encode($customer);
    } else {
        errorResponse(404, 'Customer not found');
    }
}

// ─────────────────────────────────────────────
// POST — create a new customer
// Endpoint: POST /api/customers.php
// Body (JSON): {"name":"...","email":"...","phone":"...","plan_id":2}
// ─────────────────────────────────────────────
function createCustomer($conn) {
    $body = json_decode(file_get_contents('php://input'), true);
    if (!$body || !isset($body['name']) || !isset($body['email'])) {
        errorResponse(400, 'Name and email are required');
        return;
    }
    $name    = mysqli_real_escape_string($conn, $body['name']);
    $email   = mysqli_real_escape_string($conn, $body['email']);
    $phone   = mysqli_real_escape_string($conn, $body['phone'] ?? '');
    $plan_id = (int)($body['plan_id'] ?? 1);

    $stmt = mysqli_prepare($conn,
        "INSERT INTO customers (name, email, phone, plan_id, status)
         VALUES (?, ?, ?, ?, 'active')");
    mysqli_stmt_bind_param($stmt, 'sssi', $name, $email, $phone, $plan_id);
    if (mysqli_stmt_execute($stmt)) {
        http_response_code(201);
        echo json_encode([
            'success' => true,
            'message' => 'Customer created successfully',
            'id'      => mysqli_insert_id($conn)
        ]);
    } else {
        errorResponse(500, 'Failed to create customer: ' . mysqli_error($conn));
    }
}

// ─────────────────────────────────────────────
// PUT — update an existing customer
// Endpoint: PUT /api/customers.php?id=5
// Body (JSON): {"name":"New Name","email":"new@email.com"}
// ─────────────────────────────────────────────
function updateCustomer($conn, $id) {
    $body = json_decode(file_get_contents('php://input'), true);
    if (!$body) { errorResponse(400, 'No data provided'); return; }

    $name    = mysqli_real_escape_string($conn, $body['name']    ?? '');
    $email   = mysqli_real_escape_string($conn, $body['email']   ?? '');
    $phone   = mysqli_real_escape_string($conn, $body['phone']   ?? '');
    $plan_id = (int)($body['plan_id'] ?? 1);

    $stmt = mysqli_prepare($conn,
        "UPDATE customers SET name=?, email=?, phone=?, plan_id=?
         WHERE id=?");
    mysqli_stmt_bind_param($stmt, 'sssii', $name, $email, $phone, $plan_id, $id);
    if (mysqli_stmt_execute($stmt) && mysqli_stmt_affected_rows($stmt) > 0) {
        http_response_code(200);
        echo json_encode(['success' => true, 'message' => 'Customer updated successfully']);
    } else {
        errorResponse(404, 'Customer not found or no changes made');
    }
}

// ─────────────────────────────────────────────
// DELETE — remove a customer
// Endpoint: DELETE /api/customers.php?id=5
// ─────────────────────────────────────────────
function deleteCustomer($conn, $id) {
    $stmt = mysqli_prepare($conn, "DELETE FROM customers WHERE id = ?");
    mysqli_stmt_bind_param($stmt, 'i', $id);
    if (mysqli_stmt_execute($stmt) && mysqli_stmt_affected_rows($stmt) > 0) {
        http_response_code(200);
        echo json_encode(['success' => true, 'message' => 'Customer deleted successfully']);
    } else {
        errorResponse(404, 'Customer not found');
    }
}

// ─────────────────────────────────────────────
// Helper: send a JSON error response
// ─────────────────────────────────────────────
function errorResponse($code, $message) {
    http_response_code($code);
    echo json_encode(['success' => false, 'message' => $message]);
}

Open in browser — test GET endpoints immediately

# Get all active customers
http://localhost/your-project-name/api/customers.php

# Get customer with ID 1
http://localhost/your-project-name/api/customers.php?id=1

JavaScript fetch() — call your PHP API from any frontend

// ── GET all customers ──────────────────────────────────
fetch('http://localhost/your-project/api/customers.php')
  .then(res => res.json())
  .then(customers => {
    customers.forEach(c => console.log(c.name, c.plan_name));
  });

// ── POST — create a new customer ──────────────────────
fetch('http://localhost/your-project/api/customers.php', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    name:    'Sarah Jones',
    email:   'sarah@example.com',
    phone:   '07700900123',
    plan_id: 2
  })
})
.then(res => res.json())
.then(data => {
  if (data.success) {
    console.log('Created customer with ID:', data.id);
  }
});

// ── DELETE a customer ─────────────────────────────────
fetch('http://localhost/your-project/api/customers.php?id=42', {
  method: 'DELETE'
})
.then(res => res.json())
.then(data => console.log(data.message));

Android Java — HTTP GET request using OkHttp (most common Android HTTP library)

// Add OkHttp to your build.gradle:
// implementation 'com.squareup.okhttp3:okhttp:4.12.0'

OkHttpClient client = new OkHttpClient();

// GET all customers from your PHP API
Request request = new Request.Builder()
    .url("http://10.0.2.2/your-project/api/customers.php")
    // Note: 10.0.2.2 = localhost when running in Android emulator
    // For real devices on same network: use your computer's IP address
    .build();

client.newCall(request).enqueue(new Callback() {
    @Override public void onResponse(Call call, Response response) throws IOException {
        String jsonData = response.body().string();
        // Parse the JSON data here using Gson or org.json
        // JSONArray customers = new JSONArray(jsonData);
    }
    @Override public void onFailure(Call call, IOException e) {
        e.printStackTrace();
    }
});

SQL Adapt the getAllCustomers() query for the bills table

-- Original customers query:
SELECT c.id, c.name, c.email, c.status, p.plan_name, p.price
FROM customers c
LEFT JOIN internet_plans p ON c.plan_id = p.id
WHERE c.status = 'active'

-- Adapted for bills table:
SELECT b.id, b.amount, b.month, b.status,
       c.name AS customer_name,
       c.email AS customer_email
FROM bills b
JOIN customers c ON b.customer_id = c.id
ORDER BY b.month DESC, c.name ASC

-- Adapted for doctors table (hospital system):
SELECT d.id, d.name, d.specialization, d.phone,
       w.ward_name
FROM doctors d
LEFT JOIN wards w ON d.ward_id = w.id
ORDER BY d.name ASC