Menggenerate nomor id

<?php

//config
$database = "dopo";
$tabel = "po";
$kolom_generate ="id";
$kolom_referensi = "id";

/* Database connection start */
$servername = "localhost";
$username = "root";
$password = "";
$dbname = $database;

$mysqli = mysqli_connect($servername, $username, $password, $dbname) or die("Connection failed: " . mysqli_connect_error());
$q1 = "select * from $tabel order by $kolom_referensi DESC";
/* Database connection end */


echo '<table>';
// connect to the database


// number of results to show per page
$per_page = 10000;

// figure out the total pages in the database
if ($result = $mysqli->query($q1))
{
if ($result->num_rows != 0)
{
$total_results = $result->num_rows;
// ceil() returns the next highest integer value by rounding up value if necessary
$total_pages = ceil($total_results / $per_page);

// check if the 'page' variable is set in the URL (ex: view-paginated.php?page=1)
if (isset($_GET['page']) && is_numeric($_GET['page']))
{
$show_page = $_GET['page'];

// make sure the $show_page value is valid
if ($show_page > 0 && $show_page <= $total_pages)
{
$start = ($show_page -1) * $per_page;
$end = $start + $per_page;
}
else
{
// error - show first set of results
$start = 0;
$end = $per_page;
}
}
else
{
// if page isn't set, show first set of results
$start = 0;
$end = $per_page;
}

// display pagination
for ($i = 1; $i <= $total_pages; $i++){if (isset($_GET['page']) && $_GET['page'] == $i){}else{
}
}

//-------------------- loop through results of database query, displaying them in the table
for ($i = $start; $i < $end; $i++)
{
// make sure that PHP doesn't try to show results that don't exist
if ($i == $total_results) { break; }

// find specific row
$result->data_seek($i);
$row = $result->fetch_row();

// nomor urut tabel tampilan
// echo out the contents of each row into a table
$pin = bin2hex(random_bytes(4)) . '-' . bin2hex(random_bytes(2)) . '-' . bin2hex(random_bytes(2)) . '-' . bin2hex(random_bytes(2)) . '-' . bin2hex(random_bytes(6));
$query_2 = "UPDATE $tabel SET $kolom_generate ='$pin' WHERE $kolom_referensi = '".$row[0]."' ";
/* $query_1 = "UPDATE $tabel SET $kolom_generate ='$i'"; */
echo "UPDATE $tabel SET $kolom_generate ='$pin' WHERE $kolom_referensi = '".$row[0]."'  </br>" ;
mysqli_query($mysqli, $query_2);
}
echo "</tbody>";
echo "</table>";

}
else
{
echo " Tidak Ada Data";

}
}
// error with the query
else
{
echo "Error: " . $mysqli->error;
echo "Halo";
}

// close database connHection
$mysqli->close();

?>