class FlowSensor {
  final int id;
  final double flowRate;
  final double volume;

  FlowSensor({required this.id, required this.flowRate, required this.volume});

  factory FlowSensor.fromJson(Map<String, dynamic> json) {
    return FlowSensor(
      id: json['sensor_id'],
      flowRate: json['flow_rate'].toDouble(),
      volume: json['total_volume'].toDouble(),
    );
  }
}
-----------------------------------------
<?php
$conn = new mysqli("localhost", "db_user", "db_pass", "flow_db");
$data = json_decode(file_get_contents('php://input'), true);

if ($data) {
    foreach ($data as $sensor) {
        $id = $sensor['id'];
        $rate = $sensor['flow_rate'];
        $vol = $sensor['volume'];
        $sql = "INSERT INTO flow_logs (sensor_id, flow_rate, total_volume) 
                VALUES ($id, $rate, $vol) 
                ON DUPLICATE KEY UPDATE flow_rate=$rate, total_volume=$vol";
        $conn->query($sql);
    }
    echo json_encode(["status" => "success"]);
}
$conn->close();
?>
--------------------------------------------------
#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>

const char* ssid = "YOUR_WIFI_SSID";
const char* password = "YOUR_WIFI_PASSWORD";
const char* serverUrl = "http://your-server-ip/api/upload_flow.php";

const int SENSOR_PINS[] = {32, 33, 25, 26, 27};
volatile long pulseCounts[] = {0, 0, 0, 0, 0};
float calibrationFactor = 7.5; // YF-S201 constant

// IRAM_ATTR is required for ESP32 interrupt routines
void IRAM_ATTR isr0() { pulseCounts[0]++; }
void IRAM_ATTR isr1() { pulseCounts[1]++; }
void IRAM_ATTR isr2() { pulseCounts[2]++; }
void IRAM_ATTR isr3() { pulseCounts[3]++; }
void IRAM_ATTR isr4() { pulseCounts[4]++; }

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  
  void (*isrFuncs[])() = {isr0, isr1, isr2, isr3, isr4};
  for (int i = 0; i < 5; i++) {
    pinMode(SENSOR_PINS[i], INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(SENSOR_PINS[i]), isrFuncs[i], FALLING);
  }
}

void loop() {
  static unsigned long lastMillis = 0;
  if (millis() - lastMillis > 5000) { // Send data every 5 seconds
    lastMillis = millis();
    
    StaticJsonDocument<512> doc;
    JsonArray data = doc.to<JsonArray>();

    for (int i = 0; i < 5; i++) {
      float flowRate = (pulseCounts[i] / calibrationFactor); // L/min
      float totalVolume = pulseCounts[i] / 450.0; // 450 pulses per Liter
      
      JsonObject sensor = data.createNestedObject();
      sensor["id"] = i + 1;
      sensor["flow_rate"] = flowRate;
      sensor["volume"] = totalVolume;
    }

    String jsonString;
    serializeJson(doc, jsonString);

    if (WiFi.status() == WL_CONNECTED) {
      HTTPClient http;
      http.begin(serverUrl);
      http.addHeader("Content-Type", "application/json");
      int httpResponseCode = http.POST(jsonString);
      http.end();
    }
  }
}