PHP pagination class

<?php
class pagination
{
 public function __construct()
 {
 }
 public function calculate_pages($total_rows, $rows_per_page, $page_num)
 {
  $arr = array();
  // calculate last page
  $last_page = ceil($total_rows / $rows_per_page);
  // make sure we are within limits
  $page_num = (int) $page_num;
  if ($page_num < 1)
  {
     $page_num = 1;
  } 
  elseif ($page_num > $last_page)
  {
     $page_num = $last_page;
  }
  $upto = ($page_num - 1) * $rows_per_page;
  $arr['limit'] = 'LIMIT '.$upto.',' .$rows_per_page;
  $arr['current'] = $page_num;
  if ($page_num == 1)
   $arr['previous'] = $page_num;
  else
   $arr['previous'] = $page_num - 1;
  if ($page_num == $last_page)
   $arr['next'] = $last_page;
  else
   $arr['next'] = $page_num + 1;
  $arr['last'] = $last_page;
  $arr['info'] = 'Page ('.$page_num.' of '.$last_page.')';
  $arr['pages'] = $this->get_surrounding_pages($page_num, $last_page, $arr['next']);
  return $arr;
 }
 function get_surrounding_pages($page_num, $last_page, $next)
 {
  $arr = array();
  $show = 5; // how many boxes
  // at first
  if ($page_num == 1)
  {
   // case of 1 page only
   if ($next == $page_num) return array(1);
   for ($i = 0; $i < $show; $i++)
   {
    if ($i == $last_page) break;
    array_push($arr, $i + 1);
   }
   return $arr;
  }
  // at last
  if ($page_num == $last_page)
  {
   $start = $last_page - $show;
   if ($start < 1) $start = 0;
   for ($i = $start; $i < $last_page; $i++)
   {
    array_push($arr, $i + 1);
   }
   return $arr;
  }
  // at middle
  $start = $page_num - $show;
  if ($start < 1) $start = 0;
  for ($i = $start; $i < $page_num; $i++)
  {
   array_push($arr, $i + 1);
  }
  for ($i = ($page_num + 1); $i < ($page_num + $show); $i++)
  {
   if ($i == ($last_page + 1)) break;
   array_push($arr, $i);
  }
  return $arr;
 }
}
?>

Usage

Simple and raw. No theory, plain code. This is it, PHP pagination class, one of the most wanted snippets for web applications.
How to use it:

Instantiate the class (PHP5 version):

$p = new pagination();

Run the first query to select the number of total rows and call the first function,
with arguments the total rows number, how many rows to show per page and current page number:


$arr = $p->calculate_pages(70, 10, 1);

This function will call the second one in the class to get the surrounding pages of the page 
we are requesting.
The returned result should look like this:

Array
(
[limit] => LIMIT 0,10
[current] => 1
[previous] => 1
[next] => 2
[last] => 7
[info] => Page (1 of 7)
[pages] => Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
)
)

// at middle
$start = $page_num - ceil($show / 2);
$end = $page_num + floor($show / 2 );
if ($end >= $last_page) $start = $last_page - $show;
if ($start < 0) { $start = 0; $end = $show; }
for ($i = $start; $i < $end; $i++)
{
if ($i == $last_page) break;
array_push($arr, $i + 1);
}
return $arr;

*****************************************(OR)*****************************

// at middle
$start = $page_num - $show / 2;
if ($start < 1) $start = 0;
if ($last_page- $page_num == 1){
$arr[] = array("p"=> floor($start));
}
for ($i = $start; $i < $page_num; $i++) {
$arr[] = array("p"=>floor($i + 1));
}

for ($i = ($page_num + 1); $i < ($page_num + $show / 2 + 1); $i++) {
if ($i == ($last_page + 1)) break;
$arr[] = array("p"=>floor($i));
}

$a = array();
$i = 0;
foreach ($arr as $page){
if ($i++ < $show) $a[] = $page;
}

-------------------------------------------------------------------------------------------------------------------------------------

I tested it using this code below but I got this 

ERROR: "Fatal error: Cannot pass parameter 3 by reference on line $arr = $p->calculate_pages( $result, 10, 1 );"

How to resolve this? ;)

<?php
require_once( 'classes/connection.php' );
require_once( 'classes/php-pagination-class.php' );
$p = new pagination();
$qry = mysql_query( "SELECT * FROM items" ); 
$result = mysql_num_rows( $qry );
$arr = $p->calculate_pages( $result, 10, 1 );
echo "";
echo print_r( $arr );
echo "";
?>