Smart pagination algorithm [closed]

StackOverflow https://stackoverflow.com/questions/163809

  •  03-07-2019
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Question

I'm looking for an example algorithm of smart pagination. By smart, what I mean is that I only want to show, for example, 2 adjacent pages to the current page, so instead of ending up with a ridiculously long page list, I truncate it.

Here's a quick example to make it clearer... this is what I have now:

Pages: 1 2 3 4 [5] 6 7 8 9 10 11

This is what I want to end up with:

Pages: ... 3 4 [5] 6 7 ...

(In this example, I'm only showing 2 adjacent pages to the current page)

I'm implementing it in PHP/Mysql, and the "basic" pagination (no trucating) is already coded, I'm just looking for an example to optimize it... It can be an example in any language, as long as it gives me an idea as to how to implement it...

Was it helpful?

Solution

I had the same need a while ago.

Here's the article I used to get it done (with PHP code): Digg-Style Pagination

It works pretty fast and has some additions to what you're trying to do, like:

[1] 2 3 4 5 6 ... 100
1 [2] 3 4 5 6 ... 100
...
1 ... 4 5 [6] 7 8 ... 100

Here is the code from the broken link:

<?php
    /*
        Place code to connect to your DB here.
    */

    // How many adjacent pages should be shown on each side?
    $adjacents = 3;

    /* 
       First get total number of rows in data table. 
       If you have a WHERE clause in your query, make sure you mirror it here.
    */
    $query = "SELECT COUNT(*) as num FROM portfolio";
    $total_pages = mysql_fetch_array(mysql_query($query));
    $total_pages = $total_pages[num];

    /* Setup vars for query. */
    $limit = 2;                                 //how many items to show per page
    if($page) 
        $start = ($page - 1) * $limit;          //first item to display on this page
    else
        $start = 0;                             //if no page var is given, set start to 0

    /* Get data. */
    $query = "SELECT category, uname, title FROM portfolio LIMIT $start, $limit";
    $portfolio = mysql_query($query);

    /* Setup page vars for display. */
    if ($page == 0) $page = 1;                  //if no page var is given, default to 1.
    $prev = $page - 1;                          //previous page is page - 1
    $next = $page + 1;                          //next page is page + 1
    $lastpage = ceil($total_pages/$limit);      //lastpage is = total pages / items per page, rounded up.
    $lpm1 = $lastpage - 1;                      //last page minus 1

    /* 
        Now we apply our rules and draw the pagination object. 
        We're actually saving the code to a variable in case we want to draw it more than once.
    */
    $pagination = "";
    if($lastpage > 1)
    {   
        $pagination .= "<div class="\"pagination\"">";
        //previous button
        if ($page > 1) 
            $pagination.= "<a href="\"diggstyle.php?page=$prev\"">« previous</a>";
        else
            $pagination.= "<span class="\"disabled\"">« previous</span>";   

        //pages 
        if ($lastpage < 7 + ($adjacents * 2))   //not enough pages to bother breaking it up
        {   
            for ($counter = 1; $counter <= $lastpage; $counter++)
            {
                if ($counter == $page)
                    $pagination.= "<span class="\"current\"">$counter</span>";
                else
                    $pagination.= "<a href="\"diggstyle.php?page=$counter\"">$counter</a>";                 
            }
        }
        elseif($lastpage > 5 + ($adjacents * 2))    //enough pages to hide some
        {
            //close to beginning; only hide later pages
            if($page < 1 + ($adjacents * 2))        
            {
                for ($counter = 1; $counter < 4 + ($adjacents * 2); $counter++)
                {
                    if ($counter == $page)
                        $pagination.= "<span class="\"current\"">$counter</span>";
                    else
                        $pagination.= "<a href="\"diggstyle.php?page=$counter\"">$counter</a>";                 
                }
                $pagination.= "...";
                $pagination.= "<a href="\"diggstyle.php?page=$lpm1\"">$lpm1</a>";
                $pagination.= "<a href="\"diggstyle.php?page=$lastpage\"">$lastpage</a>";       
            }
            //in middle; hide some front and some back
            elseif($lastpage - ($adjacents * 2) > $page && $page > ($adjacents * 2))
            {
                $pagination.= "<a href="\"diggstyle.php?page=1\"">1</a>";
                $pagination.= "<a href="\"diggstyle.php?page=2\"">2</a>";
                $pagination.= "...";
                for ($counter = $page - $adjacents; $counter <= $page + $adjacents; $counter++)
                {
                    if ($counter == $page)
                        $pagination.= "<span class="\"current\"">$counter</span>";
                    else
                        $pagination.= "<a href="\"diggstyle.php?page=$counter\"">$counter</a>";                 
                }
                $pagination.= "...";
                $pagination.= "<a href="\"diggstyle.php?page=$lpm1\"">$lpm1</a>";
                $pagination.= "<a href="\"diggstyle.php?page=$lastpage\"">$lastpage</a>";       
            }
            //close to end; only hide early pages
            else
            {
                $pagination.= "<a href="\"diggstyle.php?page=1\"">1</a>";
                $pagination.= "<a href="\"diggstyle.php?page=2\"">2</a>";
                $pagination.= "...";
                for ($counter = $lastpage - (2 + ($adjacents * 2)); $counter <= $lastpage; $counter++)
                {
                    if ($counter == $page)
                        $pagination.= "<span class="\"current\"">$counter</span>";
                    else
                        $pagination.= "<a href="\"diggstyle.php?page=$counter\"">$counter</a>";                 
                }
            }
        }

        //next button
        if ($page < $counter - 1) 
            $pagination.= "<a href="\"diggstyle.php?page=$next\"">next »</a>";
        else
            $pagination.= "<span class="\"disabled\"">next »</span>";
        $pagination.= "</div>\n";       
    }
?>
<ul>
    <?php
        while($item = mysql_fetch_array($portfolio))
        {
    ?>
        <li><a href="/web/20080709045706/http://www.strangerstudios.com/portfolio//"></a></li>
    <?php
        }
    ?>
</ul>
<?=$pagination?>

OTHER TIPS

Kinda late =), but here is my go at it:

function Pagination($data, $limit = null, $current = null, $adjacents = null)
{
    $result = array();

    if (isset($data, $limit) === true)
    {
        $result = range(1, ceil($data / $limit));

        if (isset($current, $adjacents) === true)
        {
            if (($adjacents = floor($adjacents / 2) * 2 + 1) >= 1)
            {
                $result = array_slice($result, max(0, min(count($result) - $adjacents, intval($current) - ceil($adjacents / 2))), $adjacents);
            }
        }
    }

    return $result;
}

Example:

$total = 1024;
$per_page = 10;
$current_page = 2;
$adjacent_links = 4;

print_r(Pagination($total, $per_page, $current_page, $adjacent_links));

Output (@ Codepad):

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

Another example:

$total = 1024;
$per_page = 10;
$current_page = 42;
$adjacent_links = 4;

print_r(Pagination($total, $per_page, $current_page, $adjacent_links));

Output (@ Codepad):

Array
(
    [0] => 40
    [1] => 41
    [2] => 42
    [3] => 43
    [4] => 44
)

I started from the lazaro's post and tried to make a robust and light algorithm with javascript/jquery... No additional and/or bulky pagination libraries needed... Look on fiddle for an live example: http://jsfiddle.net/97JtZ/1/

var totalPages = 50, buttons = 5;
var currentPage = lowerLimit = upperLimit = Math.min(9, totalPages);

//Search boundaries
for (var b = 1; b < buttons && b < totalPages;) {
    if (lowerLimit > 1 ) { lowerLimit--; b++; }
    if (b < buttons && upperLimit < totalPages) { upperLimit++; b++; }
}

//Do output to a html element
for (var i = lowerLimit; i <= upperLimit; i++) {
    if (i == currentPage) $('#pager').append('<li>' + i + '</li> ');
    else $('#pager').append('<a href="#"><li><em>' + i + '</em></li></a> ');
}

I made a pagination class and put in on Google Code a while ago. Check it out its pretty simple http://code.google.com/p/spaceshipcollaborative/wiki/PHPagination

$paging = new Pagination();
$paging->set('urlscheme','class.pagination.php?page=%page%');
$paging->set('perpage',10);
$paging->set('page',15);
$paging->set('total',3000);
$paging->set('nexttext','Next Page');
$paging->set('prevtext','Previous Page');
$paging->set('focusedclass','selected');
$paging->set('delimiter','');
$paging->set('numlinks',9);
$paging->display();

List<int> pages = new List<int>();
int pn = 2; //example of actual pagenumber
int total = 8;

for(int i = pn - 9; i <= pn + 9; i++)
{
  if(i < 1) continue;
  if(i > total) break;
  pages.Add(i);
}

return pages;

I would use something simple on the page you are showing the paginator, like:

if (
  $page_number == 1 || $page_number == $last_page ||
  $page_number == $actual_page ||
  $page_number == $actual_page+1 || $page_number == $actual_page+2 ||
  $page_number == $actual_page-1 || $page_number == $actual_page-2
  ) echo $page_number;

You can adapt it to show each 10 or so pages with % operator ...

I think using switch() case would be better in this case, I just don't remember the syntax now

Keep it Simple :)

If it's possible to generate the pagination on the client, I would suggest my new Pagination plugin: http://www.xarg.org/2011/09/jquery-pagination-revised/

The solution to your question would be:

$("#pagination").paging(1000, { // Your number of elements
        format: '. - nncnn - ', // Format to get Pages: ... 3 4 [5] 6 7 ...
        onSelect: function (page) {
                // add code which gets executed when user selects a page
        },
        onFormat: function (type) {
                switch (type) {
                case 'block': // n and c
                        return '<a>' + this.value + '</a>';
                case 'fill': // -
                        return '...';
                case 'leap': // .
                        return 'Pages:';
                }
        }
});

The code of the CodeIgniter pagination-class can be found on GitHub

(what you call) Smart pagination can be achieved by configuration.

$config['num_links'] = 2;

The number of "digit" links you would like before and after the selected page number. For example, the number 2 will place two digits on either side, as in the example links at the very top of this page.

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