PHP pagination error with only 1 page - php

Question

I have a problem with pagination, i see only first page, i try to undestand. I have a file HTML with a script and the script launch a file php. But the result is only a file
<?php
include 'database.php';
$output = '';
$start=0;
$limit=2;
if(isset($_GET['id'])){
$id=$_GET['id'];
$start=($id-1)*$limit;
}else{
$id=1;
}
$search = $_POST["search"];
if($search == ''){
$sql = "SELECT * FROM dati ORDER BY id DESC LIMIT $start, $limit";
}
else {
$sql = "SELECT * FROM dati WHERE nome LIKE '%".$_POST["search"]."%' ORDER BY id DESC LIMIT $start, $limit";
}
$retval = mysqli_query( $dbconfig, $sql);
$output .= '
<table class="table table-striped table-bordered">
<thead>
<tr>
<th>Nome</th>
<th>Categoria</th>
<th>Numero di Telefono</th>
</tr>
</thead>
<tbody>';
while($row=mysqli_fetch_array($retval)){
$output .= '
<tr>
<td>'. $row['nome'] . '</td>
<td>'. $row['categoria'] . '</td>
<td>'. $row['telefono'] . '</td>
</tr>';
}
$output .= '
</tbody>
</table>';
$ret = mysqli_num_rows(mysqli_query( $dbconfig, $sql));
$total=ceil($ret/$limit);
$output .= '
<div class="row">
<ul class="page">';
for($i=1;$i<=$total;$i++){
if($i==$id) {
$output .= '<li class="corrente">'.$i.'</li>';
}else {
$output .= '<li><a href=?id='.$i.'>'.$i.'</a></li>';
}
}
$output .= '
</ul>
</div>';
echo $output;
?>
This is file PHP with pagination but nothing
<input type="submit" name="test" id="test" value="Ricerca">