php 8 having issues with generating pdf code example

Example: php create pdf

<?php
//install Dompdf library at link below:
//https://github.com/dompdf/dompdf
use Dompdf\Dompdf;
session_start();

  // Include the database
  $servername = "";
  $username = "";
  $password = "";
  $dbname = "";

  // Create connection
  $conn = new mysqli($servername, $username, $password, $dbname);
  // Check connection
  if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
  }  

    $html = '<table border=1>';	
    $html .= '<thead>';
    $html .= '<tr>';
    $html .= '<th>ID</th>';
    $html .= '<th>Collum1</th>';
    $html .= '<th>Collum2</th>';
    $html .= '<th>Collum3</th>';
    $html .= '</tr>';
    $html .= '</thead>';
    $html .= '<tbody>';
    
    $sql = "SELECT * FROM tableName";
    $sql = mysqli_query($conn, $sql);
    while($row = mysqli_fetch_assoc($sql)){      
      $html = ''; // your html code		
    }   

    // include autoloader
    require_once("dompdf/autoload.inc.php");

    //Create instance
    $dompdf = new DOMPDF();
    
    // Upload your HTML code
    $dompdf->load_html('
        <h1 style="text-align: center;">RentCar</h1>
        '. $html .'
      ');

    //Render html
    $dompdf->render();

    //Create and output the pdf 
    $pdf = $dompdf->output();

    //Visualize the page
    $dompdf->stream(
      "form.pdf", 
      array(
        "Attachment" => false //To download turn it to true, to preview pdf turn it to false
      )
    );

?>