Pagination for category in php - php

Question

I wrote a code pagination for category in php, this should display all items from database by selecting id and category id
It's displaying only first page, but when I click second page it's not displaying other list.
Where can I fix to display all items of list?
Here is my code:
<?php
include("conn.php");
$cid=intval($_GET['cid']);
$query=mysqli_query($conn,"select count(id) from adverts where category='$cid'");
$row = mysqli_fetch_row($query);
$rows = $row[0];
$page_rows = 3;
$last = ceil($rows/$page_rows);
if($last < 1){
$last = 1;
}
$pagenum = 1;
if(isset($_GET['pn'])){
$pagenum = preg_replace('#[^0-9]#', '', $_GET['pn']);
}
if ($pagenum < 1) {
$pagenum = 1;
}
else if ($pagenum > $last) {
$pagenum = $last;
}
$limit = 'LIMIT ' .($pagenum - 1) * $page_rows .',' .$page_rows;
$query=mysqli_query($conn,"SELECT * FROM adverts WHERE category='$cid' $limit");
$paginationCtrls = '';
if($last != 1){
if ($pagenum > 1) {
$previous = $pagenum - 1;
$paginationCtrls .= 'Previous ';
for($i = $pagenum-4; $i < $pagenum; $i++){
if($i > 0){
$paginationCtrls .= ''.$i.' ';
}
}
}
$paginationCtrls .= ''.$pagenum.' ';
for($i = $pagenum+1; $i <= $last; $i++){
$paginationCtrls .= ''.$i.' ';
if($i >= $pagenum+4){
break;
}
}
if ($pagenum != $last) {
$next = $pagenum + 1;
$paginationCtrls .= ' Next ';
}
}
?>