<?php
// the page where this paging is used
$page_dom = "index.php";

echo "<ul class=\"pagination\">";

// button for first page
if ($page > 1) {
    echo "<li><a href='{$page_dom}' title='Go to the first page.'>";
    echo "First Page";
    echo "</a></li>";
}

// count all products in the database to calculate total pages
$total_rows = $product->countAll();
$total_pages = ceil($total_rows / $records_per_page);

// range of links to show
$range = 2;

// display links to 'range of pages' around 'current page'
$initial_num = $page - $range;
$condition_limit_num = ($page + $range) + 1;

for ($x = $initial_num; $x < $condition_limit_num; $x++) {
    // be sure '$x is greater than 0' AND 'less than or equal to the $total_pages'
    if (($x > 0) && ($x <= $total_pages)) {
        // current page
        if ($x == $page) {
            echo "<li class='active'><a href=\"#\">$x <span class=\"sr-only\">(current)</span></a></li>";
        }

        // not current page
        else {
            echo "<li><a href='{$page_dom}?page=$x'>$x</a></li>";
        }
    }
}

// button for last page
if ($page < $total_pages) {
    echo "<li><a href='" . $page_dom . "?page={$total_pages}' title='Last page is {$total_pages}.'>";
    echo "Last Page";
    echo "</a></li>";
}

echo "</ul>";
?>