PHP原生分页原理

<?php

  class Page {

     private $total;   //总记录

     private $pagesize;  //每页显示多少条

     private $limit;     //limit

     private $page;      //当前页码

     private $pagenum;   //总页码

     private $url;      //地址

     private $bothnum;   //两边保持数字分页的量

   //构造方法初始化

   public function __construct($_total, $_pagesize) {

     $this->total = $_total ? $_total : 1;

     $this->pagesize = $_pagesize;

     $this->pagenum = ceil($this->total / $this->pagesize);

     $this->page = $this->setPage();

     $this->limit = "LIMIT ".($this->page-1)*$this->pagesize.",$this->pagesize";

     $this->url = $this->setUrl();

     $this->bothnum = 2;

   }

   //拦截器

   private function __get($_key) {

     return $this->$_key;

   }

   //获取当前页码

   private function setPage() {

     if (!empty($_GET['page'])) {

        if ($_GET['page'] > 0) {

          if ($_GET['page'] > $this->pagenum) {

             return $this->pagenum;

          } else {

             return $_GET['page'];

          }

        } else {

          return 1;

        }

     } else {

        return 1;

     }

   }

   //获取地址

   private function setUrl() {

     $_url = $_SERVER["REQUEST_URI"];

     $_par = parse_url($_url);

     if (isset($_par['query'])) {

        parse_str($_par['query'],$_query);

        unset($_query['page']);

        $_url = $_par['path'].'?'.http_build_query($_query);

     }

     return $_url;

   }   //数字目录

   private function pageList() {

     for ($i=$this->bothnum;$i>=1;$i--) {

      $_page = $this->page-$i;

      if ($_page < 1) continue;

        $_pagelist .= ' <a href="'.$this->url.'&page='.$_page.'" rel="external nofollow" rel="external nofollow" >'.$_page.'</a> ';

     }

     $_pagelist .= ' <span class="me">'.$this->page.'</span> ';

     for ($i=1;$i<=$this->bothnum;$i++) {

      $_page = $this->page+$i;

        if ($_page > $this->pagenum) break;

        $_pagelist .= ' <a href="'.$this->url.'&page='.$_page.'" rel="external nofollow" rel="external nofollow" >'.$_page.'</a> ';

     }

     return $_pagelist;

   }

   //首页

   private function first() {

     if ($this->page > $this->bothnum+1) {

        return ' <a href="'.$this->url.'" rel="external nofollow" >1</a> ...';

     }

   }

   //上一页

   private function prev() {

     if ($this->page == 1) {

        return '<span class="disabled">上一页</span>';

     }

     return ' <a href="'.$this->url.'&page='.($this->page-1).'" rel="external nofollow" >上一页</a> ';

   }

   //下一页

   private function next() {

     if ($this->page == $this->pagenum) {

        return '<span class="disabled">下一页</span>';

     }

     return ' <a href="'.$this->url.'&page='.($this->page+1).'" rel="external nofollow" >下一页</a> ';

   }

   //尾页

   private function last() {

     if ($this->pagenum - $this->page > $this->bothnum) {

        return ' ...<a href="'.$this->url.'&page='.$this->pagenum.'" rel="external nofollow" >'.$this->pagenum.'</a> ';

     }

   }

   //分页信息

   public function showpage() {

     $_page .= $this->first();

     $_page .= $this->pageList();

     $_page .= $this->last();

     $_page .= $this->prev();

     $_page .= $this->next();

     return $_page;

   }

 }

?>

<?php

  $_page = new Page($_total,$_pagesize);

  //其中 $_total 是数据集的总条数,$_pagesize 是每页显示的数量.

?>