<?php

class Paginator
{

    /** @var int */
    private $limit = 20;

    /** @var int */
    private $page;

    /** @var int */
    private $numItems;

    /** @var int */
    private $numLinks;


    /**
     * @param int
     * @param int
     * @return void
     */
    public function __construct($numItems, $page = 1)
    {
        $this->numItems = (int) $numItems;
        $this->numLinks = $this->getNumLinks();
        $this->page = $page > 0 ? (int) $page : 1;
        if ($page > $this->numLinks) {
            $this->page = 1;
        }
    }


    /**
     * @param int
     * @return void
     */
    public function setLimit($limit)
    {
        $this->limit = $limit;
    }


    /**
     * @return int
     */
    private function getNumLinks()
    {
        return (int) floor($this->numItems / $this->limit);
    }


    /**
     * @return int
     */
    public function getOffset()
    {
        return $this->page * $this->limit;
    }


    /**
     * @param int
     * @param string|NULL
     * @param string|NULL
     * @param array
     * @param bool
     * @return string
     */
    private function getLinkHtml($page, $char = NULL, $attributes = array(), $isActive = FALSE)
    {
        if ($char === NULL) {
            $char = $page;
        }
        if ($page !== NULL) {
            $page = "?page=" . $page;
        } else {
            $page = "#";
        }

        $attrs = $this->getAttributesAsString($attributes);
        $active = "";
        if ($isActive) {
            $active = ' class="active"';
        }

        return '<a href="' . $page . '"' . $attrs . $active . '>' . $char . '</a>';
    }


    /**
     * @param string
     * @param array
     * @return string
     */
    private function getInactiveLinkHtml($char, $attributes = array())
    {
        $attrs = $this->getAttributesAsString($attributes);

        return '<span class="inactive"' . $attrs . '>' . $char . '</span>';
    }


    /**
     * @param array
     * @return string
     */
    private function getAttributesAsString(array $attributes)
    {
        $attrs = "";
        foreach ($attributes as $name => $value) {
            $attrs .= ' ' . $name . '="' . $value . '"';
        }

        return $attrs;
    }


    /**
     * @return string
     */
    public function __toString()
    {
        $list = "";

        // previous and the first page
        if ($this->page > 1) {
            $previousPage = $this->page - 1;
            $list .= $this->getLinkHtml(1, "&laquo;&laquo;", array("title" => "První stránka"));
            $list .= $this->getLinkHtml($previousPage, "&laquo;", array("title" => "Předchozí stránka"));
        } else {
            $list .= $this->getInactiveLinkHtml("&laquo;&laquo");
            $list .= $this->getInactiveLinkHtml("&laquo");
        }


        // each pages
        if ($this->numLinks === 0) {
            $list .= $this->getLinkHtml(1, NULL, array(), TRUE);
        } else {
            for ($i = -2; $i <= 2; $i++) {
                if ($i <= $this->numLinks) {
                    $page = $this->page + $i;
                    if ($page > 0 && $page <= $this->numLinks) {
                        $active = $page === $this->page;
                        $list .= $this->getLinkHtml($page, NULL, array(), $active);
                    }
                }
            }
        }


        // next and the last page
        if ($this->page < $this->numLinks) {
            $nextPage = $this->page + 1;
            $list .= $this->getLinkHtml($nextPage, "&raquo;", array("title" => "Další stránka"));
            $list .= $this->getLinkHtml($this->numLinks, "&raquo;&raquo;", array("title" => "Poslední stránka"));
        } else {
            $list .= $this->getInactiveLinkHtml("&raquo;");
            $list .= $this->getInactiveLinkHtml("&raquo;&raquo");
        }

        return <<<EOT
<div class="paginator">
    {$list}
</div>
EOT;
    }
}


// použití
$numItems = 100;
$page = isset($_GET["page"]) ? (int) $_GET["page"] : 1;

echo new Paginator($numItems, $page);