CREATE TABLE sensor_data (
  id INT(11) AUTO_INCREMENT PRIMARY KEY,
  sensor_id INT(11) NOT NULL,
  flow_rate FLOAT NOT NULL,
  volume FLOAT NOT NULL,
  timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
-------------------------------------------------
### 2. PHP Script - `insert_data.php`

```php
<?php
// --- Database Configuration ---
$servername = "YOUR_DB_SERVER";
$username = "YOUR_DB_USERNAME";
$password = "YOUR_DB_PASSWORD";
$dbname = "YOUR_DB_NAME";

// --- Create connection ---
$conn = new mysqli($servername, $username, $password, $dbname);

// --- Check connection ---
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

// --- Get JSON data from POST request ---
$json = file_get_contents('php://input');
$data = json_decode($json, true);

// --- Prepare and execute SQL statements ---
if (is_array($data)) {
  foreach ($data as $sensor => $sensorData) {
    $sensorNum = intval(substr($sensor, 6)); // Extract sensor number from key (e.g., "sensor1")
    $rate = $sensorData['rate'];
    $volume = $sensorData['volume'];
    $sql = "INSERT INTO sensor_data (sensor_id, flow_rate, volume) VALUES ($sensorNum, $rate, $volume)";
    if ($conn->query($sql) === TRUE) {
      echo "New record created successfully for sensor $sensorNum\n";
    } else {
      echo "Error: " . $sql . "<br>" . $conn->error;
    }
  }
} else {
  echo "Invalid JSON data received";
}
$conn->close();
?>
--------------------------------------------------------
To get flow rate and volume from five YF-S201 sensors on an ESP32 and send it via ArduinoJson to a PHP/MySQL backend for a Flutter app, you need ESP32 Code (C++) using interrupts (IRAM_ATTR), PHP Scripts, a MySQL Database, and Flutter code to display data, focusing on Wi-Fi connectivity, JSON serialization, HTTP POST requests, and SQL INSERT commands for data logging. The core involves ESP32 reading pulses, calculating flow (L/min) and volume (L), packaging data as JSON, sending to PHP, PHP inserting into MySQL, then Flutter fetching from PHP/MySQL. 
}
}
// Prepare JSON data
DynamicJsonDocument doc(1024); // Adjust size as needed
for (int i = 0; i < numSensors; i++) {
char sensorKey;
sprintf(sensorKey, "sensor%d", i + 1);
JsonObject sensorData = doc.createNestedObject(sensorKey);
sensorData["rate"] = currentFlowRate[i];
sensorData["volume"] = totalVolume[i];
}
String jsonString;
serializeJson(doc, jsonString); 
// Send data to PHP script
if (WiFi.status() == WL_CONNECTED) {
HTTPClient http;
http.begin(serverUrl);
http.addHeader("Content-Type", "application/json");
int httpResponseCode = http.POST(jsonString);
if (httpResponseCode > 0) {
Serial.print("HTTP Response code: ");
Serial.println(httpResponseCode);
String payload = http.getString();
Serial.println(payload);
} else {
Serial.print("Error sending data: ");
Serial.println(httpResponseCode);
}
http.end();
} else {
Serial.println("WiFi Disconnected");
}
lastMillis = millis();
}
delay(10); // Short delay to prevent watchdog timer issues
}
-------------------------------
// --- Example Flutter Code Snippets ---
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:flutter/material.dart';

class SensorData {
  final int sensorId;
  final double flowRate;
  final double volume;

  SensorData({required this.sensorId, required this.flowRate, required this.volume});

  factory SensorData.fromJson(Map<String, dynamic> json, int sensorId) {
    return SensorData(
      sensorId: sensorId,
      flowRate: json['rate'] as double,
      volume: json['volume'] as double,
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<SensorData> sensorDataList = [];
  bool isLoading = true;

  @override
  void initState() {
    super.initState();
    fetchSensorData();
  }

  Future<void> fetchSensorData() async {
    setState(() {
      isLoading = true;
    });
    try {
      final response = await http.get(Uri.parse('http://YOUR_SERVER_IP/api/get_data.php')); // Replace with your PHP script URL

      if (response.statusCode == 200) {
        final Map<String, dynamic> jsonResponse = jsonDecode(response.body);
        List<SensorData> fetchedData = [];
        jsonResponse.forEach((key, value) {
          int sensorId = int.parse(key.replaceAll('sensor', ''));
          fetchedData.add(SensorData.fromJson(value, sensorId));
        });

        setState(() {
          sensorDataList = fetchedData;
          isLoading = false;
        });
      } else {
        print('Failed to load data. Status code: ${response.statusCode}');
        setState(() {
          isLoading = false;
        });
      }
    } catch (e) {
      print('Error fetching data: $e');
      setState(() {
        isLoading = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Sensor Data'),
      ),
      body: isLoading
          ? Center(child: CircularProgressIndicator())
          : ListView.builder(
              itemCount: sensorDataList.length,
              itemBuilder: (context, index) {
                final sensorData = sensorDataList[index];
                return Card(
                  child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text('Sensor ID: ${sensorData.sensorId}'),
                        Text('Flow Rate: ${sensorData.flowRate.toStringAsFixed(2)} L/min'),
                        Text('Volume: ${sensorData.volume.toStringAsFixed(2)} L'),
                      ],
                    ),
                  ),
                );
              },
            ),
      floatingActionButton: FloatingActionButton(
        onPressed: fetchSensorData,
        tooltip: 'Refresh Data',
        child: Icon(Icons.refresh),
      ),
    );
  }
}
-----------------------------------
<?php
// --- Database Configuration (same as insert_data.php) ---
$servername = "YOUR_DB_SERVER";
$username = "YOUR_DB_USERNAME";
$password = "YOUR_DB_PASSWORD";
$dbname = "YOUR_DB_NAME";

// --- Create connection ---
$conn = new mysqli($servername, $username, $password, $dbname);

// --- Check connection ---
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

// --- Fetch the latest data for each sensor ---
$sql = "SELECT sensor_id, flow_rate, volume FROM sensor_data GROUP BY sensor_id ORDER BY timestamp DESC";
$result = $conn->query($sql);

$sensorData = array();
if ($result->num_rows > 0) {
  while($row = $result->fetch_assoc()) {
    $sensorId = "sensor" . $row["sensor_id"];
    $sensorData[$sensorId] = array(
      "rate" => floatval($row["flow_rate"]),
      "volume" => floatval($row["volume"])
    );
  }
}
header('Content-Type: application/json');
echo json_encode($sensorData);
$conn->close();
?>