一个分页导航类

<?php
// +----------------------------------------------------------------------+
// | PHP Version 4                                                        |
// +----------------------------------------------------------------------+
// | Copyright (c) 1997-2002 The PHP Group                                |
// +----------------------------------------------------------------------+
// | This source file is subject to version 2.02 of the PHP license,      |
// | that is bundled with this package in the file LICENSE, and is        |
// | available at through the world-wide-web at                           |
// | http://www.php.net/license/2_02.txt.                                 |
// | If you did not receive a copy of the PHP license and are unable to   |
// | obtain it through the world-wide-web, please send a note to          |
// | license@php.net so we can mail you a copy immediately.               |
// +----------------------------------------------------------------------+
// | Authors: Richard Heyes <richard@phpguru.org>                         |
// +----------------------------------------------------------------------+

/**
* Pager class
*
* Handles paging a set of data. For usage see the example.php provided.
*
*/

class Pager {

    /**
    * Current page
    * @var integer
    */
    var $_currentPage;

    /**
    * Items per page
    * @var integer
    */
    var $_perPage;

    /**
    * Total number of pages
    * @var integer
    */
    var $_totalPages;

    /**
    * Item data. Numerically indexed array...
    * @var array
    */
    var $_itemData;

    /**
    * Total number of items in the data
    * @var integer
    */
    var $_totalItems;

    /**
    * Page data generated by this class
    * @var array
    */
    var $_pageData;

    /**
    * Constructor
    *
    * Sets up the object and calculates the total number of items.
    *
    * @param $params An associative array of parameters This can contain:
    *                  currentPage   Current Page number (optional)
    *                  perPage       Items per page (optional)
    *                  itemData      Data to page
    */
    function pager($params = array())
    {
        global $HTTP_GET_VARS;

        $this->_currentPage = max((int)@$HTTP_GET_VARS[@#pageID@#], 1);
        $this->_perPage     = 8;
        $this->_itemData    = array();

        foreach ($params as $name => $value) {
            $this->{@#_@# . $name} = $value;
        }

        $this->_totalItems = count($this->_itemData);
    }

    /**
    * Returns an array of current pages data
    *
    * @param $pageID Desired page ID (optional)
    * @return array Page data
    */
    function getPageData($pageID = null)
    {
        if (isset($pageID)) {
            if (!empty($this->_pageData[$pageID])) {
                return $this->_pageData[$pageID];
            } else {
                return FALSE;
            }
        }

        if (!isset($this->_pageData)) {
            $this->_generatePageData();
        }

        return $this->getPageData($this->_currentPage);
    }

    /**
    * Returns pageID for given offset
    *
    * @param $index Offset to get pageID for
    * @return int PageID for given offset
    */
    function getPageIdByOffset($index)
    {
        if (!isset($this->_pageData)) {
            $this->_generatePageData();
        }

        if (($index % $this->_perPage) > 0) {
            $pageID = ceil((float)$index / (float)$this->_perPage);
        } else {
            $pageID = $index / $this->_perPage;
        }

        return $pageID;
    }

    /**
    * Returns offsets for given pageID. Eg, if you
    * pass it pageID one and your perPage limit is 10
    * it will return you 1 and 10. PageID of 2 would
    * give you 11 and 20.
    *
    * @params pageID PageID to get offsets for
    * @return array  First and last offsets
    */
    function getOffsetByPageId($pageid = null)
    {
        $pageid = isset($pageid) ? $pageid : $this->_currentPage;
        if (!isset($this->_pageData)) {
            $this->_generatePageData();
        }

        if (isset($this->_pageData[$pageid])) {
            return array(($this->_perPage * ($pageid - 1)) + 1, min($this->_totalItems, $this->_perPage * $pageid));
        } else {
            return array(0,0);
        }
    }

    /**
    * Returns back/next and page links
    *
    * @param  $back_html HTML to put inside the back link
    * @param  $next_html HTML to put inside the next link
    * @return array Back/pages/next links
    */
    function getLinks($back_html = @#<< Back@#, $next_html = @#Next >>@#)
    {
        $url   = $this->_getLinksUrl();
        $back  = $this->_getBackLink($url, $back_html);
        $pages = $this->_getPageLinks($url);
        $next  = $this->_getNextLink($url, $next_html);

        return array($back, $pages, $next, @#back@# => $back, @#pages@# => $pages, @#next@# => $next);
    }

    /**
    * Returns number of pages
    *
    * @return int Number of pages
    */
    function numPages()
    {
        return $this->_totalPages;
    }

    /**
    * Returns whether current page is first page
    *
    * @return bool First page or not
    */
    function isFirstPage()
    {
        return ($this->_currentPage == 1);
    }

    /**
    * Returns whether current page is last page
    *
    * @return bool Last page or not
    */
    function isLastPage()
    {
        return ($this->_currentPage == $this->_totalPages);
    }

    /**
    * Returns whether last page is complete
    *
    * @return bool Last age complete or not
    */
    function isLastPageComplete()
    {
        return !($this->_totalItems % $this->_perPage);
    }

    /**
    * Calculates all page data
    */
    function _generatePageData()
    {
        $this->_totalItems = count($this->_itemData);
        $this->_totalPages = ceil((float)$this->_totalItems / (float)$this->_perPage);
        $i = 1;
        if (!empty($this->_itemData)) {
            foreach ($this->_itemData as $value) {
                $this->_pageData[$i][] = $value;
                if (count($this->_pageData[$i]) >= $this->_perPage) {
                    $i++;
                }
            }
        } else {
            $this->_pageData = array();
        }
    }

    /**
    * Returns the correct link for the back/pages/next links
    *
    * @return string Url
    */
    function _getLinksUrl()
    {
        global $HTTP_SERVER_VARS;

        // Sort out query string to prevent messy urls
        $querystring = array();
        if (!empty($HTTP_SERVER_VARS[@#QUERY_STRING@#])) {
            $qs = explode(@#&@#, $HTTP_SERVER_VARS[@#QUERY_STRING@#]);            
            for ($i = 0, $cnt = count($qs); $i < $cnt; $i++) {
                list($name, $value) = explode(@#=@#, $qs[$i]);
                if ($name != @#pageID@#) {
                    $qs[$name] = $value;
                }
                unset($qs[$i]);
            }
        }
    if(is_array($qs)){
            foreach ($qs as $name => $value) {
                $querystring[] = $name . @#=@# . $value;
            }    
    }
        return $HTTP_SERVER_VARS[@#SCRIPT_NAME@#] . @#?@# . implode(@#&@#, $querystring) . (!empty($querystring) ? @#&@# : @#@#) . @#pageID=@#;
    }

    /**
    * Returns back link
    *
    * @param $url  URL to use in the link
    * @param $link HTML to use as the link
    * @return string The link
    */
    function _getBackLink($url, $link = @#<< Back@#)
    {
        // Back link
        if ($this->_currentPage > 1) {
            $back = @#<a href="@# . $url . ($this->_currentPage - 1) . @#">@# . $link . @#</a>@#;
        } else {
            $back = @#@#;
        }
        
        return $back;
    }

    /**
    * Returns pages link
    *
    * @param $url  URL to use in the link
    * @return string Links
    */
    function _getPageLinks($url)
    {
        // Create the range
        $params[@#itemData@#] = range(1, max(1, $this->_totalPages));
        $pager =& new Pager($params);
        $links =  $pager->getPageData($pager->getPageIdByOffset($this->_currentPage));

        for ($i=0; $i<count($links); $i++) {
            if ($links[$i] != $this->_currentPage) {
                $links[$i] = @#<a href="@# . $this->_getLinksUrl() . $links[$i] . @#">@# . $links[$i] . @#</a>@#;
            }
        }

        return implode(@# @#, $links);
    }

    /**
    * Returns next link
    *
    * @param $url  URL to use in the link
    * @param $link HTML to use as the link
    * @return string The link
    */
    function _getNextLink($url, $link = @#Next >>@#)
    {
        if ($this->_currentPage < $this->_totalPages) {
            $next = @#<a href="@# . $url . ($this->_currentPage + 1) . @#">@# . $link . @#</a>@#;
        } else {
            $next = @#@#;
        }

        return $next;
    }
}

?>

原文转自：http://www.ltesting.net