<p>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.</p>

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

<pre><code>Pages: 1 2 3 4 [5] 6 7 8 9 10 11
</code></pre>

<p>This is what I want to end up with:</p>

<pre><code>Pages: ... 3 4 [5] 6 7 ...
</code></pre>

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

<p>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...</p>

Here is some code based on original code from
this very old link
. It uses markup compatible with Bootstrap's pagination component, and outputs page links like this:
```
```
[1] 2 3 4 5 6 ... 100
1 [2] 3 4 5 6 ... 100
...
1 2 ... 14 15 [16] 17 18 ... 100
...
1 2 ... 97 [98] 99 100
```
```
```
```
<?php

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

//how many items to show per page
$limit = 5;

// if no page var is given, default to 1.
$page = (int)$_GET["page"] ?? 1;

//first item to display on this page
$start = ($page - 1) * $limit;

/* Get data. */
$data = $db
    ->query("SELECT * FROM mytable LIMIT $start, $limit")
    ->fetchAll();

$total_pages = count($data);

/* Setup page vars for display. */
$prev = $page - 1;
$next = $page + 1;
$lastpage = ceil($total_pages / $limit);
//last page minus 1
$lpm1 = $lastpage - 1;

$first_pages = "<li class='page-item'><a class='page-link' href='?page=1'>1</a></li>" .
    "<li class='page-item'><a class='page-link' href='?page=2'>2</a>";

$ellipsis = "<li class='page-item disabled'><span class='page-link'>...</span></li>";

$last_pages = "<li class='page-item'><a class='page-link' href='?page=$lpm1'>$lpm1</a></li>" .
    "<li class='page-item'><a class='page-link' href='?page=$lastpage'>$lastpage</a>";

$pagination = "<nav aria-label='page navigation'>";
$pagincation .= "<ul class='pagination'>";

//previous button

$disabled = ($page === 1) ? "disabled" : "";
$pagination.= "<li class='page-item $disabled'><a class='page-link' href='?page=$prev'>« previous</a></li>";

//pages 
//not enough pages to bother breaking it up
if ($lastpage < 7 + ($adjacents * 2)) { 
    for ($i = 1; $i <= $lastpage; $i++) {
        $active = $i === $page ? "active" : "";
        $pagination .= "<li class='page-item $active'><a class='page-link' href='?page=$i'>$i</a></li>";
    }
} elseif($lastpage > 5 + ($adjacents * 2)) {
    //enough pages to hide some
    //close to beginning; only hide later pages
    if($page < 1 + ($adjacents * 2)) {
        for ($i = 1; $i < 4 + ($adjacents * 2); $i++) {
            $active = $i === $page ? "active" : "";
            $pagination .= "<li class='page-item $active'><a class='page-link' href='?page=$i'>$i</a></li>";
        }
        $pagination .= $ellipsis;
        $pagination .= $last_pages;
    } elseif($lastpage - ($adjacents * 2) > $page && $page > ($adjacents * 2)) {
        //in middle; hide some front and some back
        $pagination .= $first_pages;
        $pagination .= $ellipsis
        for ($i = $page - $adjacents; $i <= $page + $adjacents; $i++) {
            $active = $i === $page ? "active" : "";
            $pagination .= "<li class='page-item $active'><a class='page-link' href='?page=$i'>$i</a></li>";
        }
        $pagination .= $ellipsis;
        $pagination .= $last_pages;
    } else {
        //close to end; only hide early pages
        $pagination .= $first_pages;
        $pagination .= $ellipsis;
        $pagination .= "<li class='page-item disabled'><span class='page-link'>...</span></li>";
        for ($i = $lastpage - (2 + ($adjacents * 2)); $i <= $lastpage; $i++) {
            $active = $i === $page ? "active" : "";
            $pagination .= "<li class='page-item $active'><a class='page-link' href='?page=$i'>$i</a></li>";
        }
    }
}

//next button
$disabled = ($page === $last) ? "disabled" : "";
$pagination.= "<li class='page-item $disabled'><a class='page-link' href='?page=$next'>next »</a></li>";

$pagination .= "</ul></nav>";

if($lastpage <= 1) {
    $pagination = "";
}

echo $pagination;

foreach ($data as $row) {
    // display your data
}

echo $pagination;
```
```