Websockets esp8266, php Workerman - how to send close signal when turning device off

I make a device on esp8266, which connects to php Workerman websocket server via websocket using WebSocketsClient.h library. Everything works, connection is established. But when I turn off the device, the server doesn't receive the onClose signal. And I need to constantly monitor whether there is a connection with the device. However, when I connect via websocket using a browser and close the tab, everything works fine and the server receives a signal that the connection is closed. How can I make the server see this when disconnecting esp8266?

Websocket server.php

<?php
require_once __DIR__ . '/vendor/autoload.php';
use Workerman\Worker;
use Workerman\Lib\Timer;


$context = array(
  'ssl' => array(
    'local_cert'  => '/etc/letsencrypt/live/***.com/fullchain.pem',
    'local_pk'    => '/etc/letsencrypt/live/***.com/privkey.pem',
    'verify_peer' => false,
    'allow_self_signed' => true,
    'verify_peer_name' => false,
  )
);



$ws_worker = new Worker("websocket://***.com:8888", $context);
$ws_worker->transport = 'ssl';

$ws_worker->onConnect = function($connection) use (&$devices)
{
    echo "Connection id: ".$connection->id.PHP_EOL;
};


$ws_worker->onClose = function($connection)  use (&$user_connections)
{
    echo '---> DISCONNECT';
};

Worker::runAll();

esp8266 code:

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <WebSocketsClient.h>


const char* ssid = "ESP32";  
const char* pwd = "01234567";  


WebSocketsClient webSocket;


void setup() {
    Serial.begin(115200);
    WiFi.begin(ssid, pwd);
    while(WiFi.status() != WL_CONNECTED){
            Serial.print(".");
            delay(100);
    }


    webSocket.beginSSL("***.com", 8888,url.c_str());
    webSocket.onEvent(webSocketEvent);
    webSocket.setReconnectInterval(5000);
}

void loop() {
  webSocket.loop();
}

void webSocketEvent(WStype_t type, uint8_t * payload, size_t length) {
   switch(type) {
        case WStype_DISCONNECTED:
            Serial.printf("Disconnected!\n");
            break;
        case WStype_CONNECTED: 
            Serial.println("SENT: Connected");
            break;
        case WStype_TEXT:
            Serial.printf("RESPONSE: %s\n", payload);
            json_error = deserializeJson(doc, payload);
            break;
        case WStype_BIN:
            Serial.printf("[WSc] get binary length: %u\n", length);
            hexdump(payload, length);
            break;
        case WStype_PING:
              Serial.printf("[WSc] get ping\n");
              break;
        case WStype_PONG:
              Serial.printf("[WSc] get pong\n");
              break;

    }
}

I tried turning on the esp8266:

webSocket.enableHeartbeat(10000, 5000, 2)

but that didn't work. When I turn off the esp8266 device, the server does not see that it is turned off.