php分页类及其实现原理

 /**
  *
  * 实现思路：分页显示拆分  :  1...上页 12 13 14 15 [16] 17 18 19 20 ...100 下页
  *
  * function htmlPart1() : 上页
  * function htmlPart2() : 1...
  * function htmlPart3() : 12 13 14 15 [16] 17 18 19 20
  * function htmlPart4() : ...100
  * function htmlPart5() : 下页
  *
  * @param int $allCount     记录总数目
  * @param int $eachPage     每页数目
  * @param int $showCount    显示数目
  * @param int $thenPage     当前页(页面传值)
  * @param string $urlPrefix Url前缀
  * @param string $urlSuffix Url后缀
  *
  * Author : [e-mail]
  * Date   : 2013.05.04
  *
  */
 class zPage {

     /** 只可内部调用 */
     private $allCount;  /** 总数(非总页数) */
     private $eachPage;  /** 每页数(分页数) */
     private $showCount; /** 显示数(显示多少页数) */
     private $urlPrefix; /** 页码前缀(例如：?page=) */
     private $urlSuffix; /** 页码后缀缀(例如：&type=1) */
     private $startHide; /** 计算前部需要出现符号(...)的最小值 */
     private $endHide;   /** 计算尾部需要出现符号(...)的最小值 */
     private $arrTxt = array(' ', ' '); // array('上页', '上页')

     /** 可外部调用 */
     public $allPage;    /** 总页数 */
     public $thenPage;   /** 当前页 */

     public function __construct($allCount, $eachPage, $showCount, $thenPage, $urlPrefix = '?page=', $urlSuffix = '') {

         $this->allCount = intval($allCount);
         $this->eachPage = intval($eachPage);
         $this->showCount = intval($showCount);
         $this->urlPrefix = trim($urlPrefix);
         $this->urlSuffix = trim($urlSuffix);

         /** 计算总页数 */
         $this->allPage = ceil($this->allCount / $this->eachPage);

         /** 使当前页的数值合法化 */
         $this->thenPage = max(intval($thenPage), 1);
         $this->thenPage >= $this->allPage AND $this->thenPage = $this->allPage;

         /** 计算前部和尾部需要出现符号(...)的最小值 */
         $this->startHide = ceil($this->showCount / 2);
         $this->endHide = $this->allPage - $this->startHide;
     }

     public function parseUrl($char = '') {

         $val = $char;
         ($char === 'prev') AND $val = $this->thenPage - 1;
         ($char === 'next') AND $val = $this->thenPage + 1;
         ($char === '') AND $val = $this->allPage;
         return $this->urlPrefix . $val . $this->urlSuffix;
     }

     public function htmlPart1() {

         $html = '';
         $this->thenPage > $this->startHide AND $html = '<a class="prev" href="' . $this->parseUrl('prev') . '" title="上一页">' . $this->arrTxt[0] . '</a>' . PHP_EOL;
         return $html;
     }

     public function htmlPart2() {

         $dot = '';
         $this->thenPage > $this->startHide AND $dot = ' ...';

         $html = '<a href="' . $this->parseUrl(1) . '">1'. $dot .'</a>' . PHP_EOL;
         $this->thenPage == 1 AND $html = '<span>1</span>' . PHP_EOL;

         return $html;
     }

     public function htmlPart3() {

         $html = '';

         if ($this->thenPage <= $this->startHide) {

             /**
              * 第一种情况：[1] 2 3 4 5 6 7 8 9 10 ...100 下页
              * 即：当前部在 不需要出现...的 范围之内
              */
             for ($i = 2, $n = $this->showCount; $i < $n; $i++) {
                 $html .= (($i == $this->thenPage) ? '<span>' . $this->thenPage . '</span>' : '<a href="' . $this->parseUrl($i) . '">' . $i . '</a>') . PHP_EOL;
             }

         } elseif ($this->thenPage >= $this->endHide) {

             /**
              * 第二种情况：上页 1..92 93 94 95 96 97 98 [99] 100
              * 即：当尾部在 不需要出现...的 范围之内
              */
             $len = $this->showCount - 2;
             $i = $this->allPage - $len;
             $n = $this->allPage;
             for ($i; $i < $n; $i++) {
                 $html .= (($i == $this->thenPage) ? '<span>' . $this->thenPage . '</span>' : '<a href="' . $this->parseUrl($i) . '">' . $i . '</a>') . PHP_EOL;
             }

         } else {

             /**
              * 第三种情况：上页 1..12 13 14 15 [16] 17 18 19 20 ...100 下页
              * 即：当前后都在 需要出现...的 范围之内
              */
             $len = $this->showCount - 2;    // 此处减去2，是说明头尾各占去一个数字(1, x)
             $offset = ceil($len / 2) - 1;   // 对剩下的数目平分，得出平分数
             $i = $this->thenPage - $offset; // 循环开始：当前页向前偏移平分数
             $n = $this->thenPage + $offset; // 循环结束：当前页向后偏移平分数
             for ($i; $i <= $n; $i++) {
                 $html .= (($i == $this->thenPage) ? '<span>' . $this->thenPage . '</span>' : '<a href="' . $this->parseUrl($i) . '">' . $i . '</a>') . PHP_EOL;
             }
         }

         return $html;
     }

     public function htmlPart4() {

         $dot = '';
         $this->thenPage < $this->endHide AND $dot = '... ';

         $html = '<a href="' . $this->parseUrl() . '">' . $dot . $this->allPage . '</a>' . PHP_EOL;
         $this->thenPage == $this->allPage AND $html = '<span>' . $this->allPage . '</span>' . PHP_EOL;

         return $html;
     }

     public function htmlPart5() {

         $html = '';
         $this->thenPage < $this->endHide AND $html = '<a class="next" href="' . $this->parseUrl('next') . '" title="下一页">' . $this->arrTxt[1] . '</a>' . PHP_EOL;
         return $html;
     }

     public function html() {

         $pageHtml = '';

         /** 总页数未达到显示页码数，则全部显示 */
         if ($this->allPage <= $this->showCount) {
             for ($i = 1; $i <= $this->allPage; $i++) {
                 $pageHtml .= ($i == $this->thenPage) ? '<span>' . $this->thenPage . '</span>' . PHP_EOL : '<a href="' . $this->parseUrl($i) . '">' . $i . '</a>' . PHP_EOL;
             }
         } else {
             $pageHtml = $this->htmlPart2() . $this->htmlPart1() . $this->htmlPart3() . $this->htmlPart4() . $this->htmlPart5();
         }

         return $pageHtml;
     }
 }

 // 调用例子
 $getPage = isset($_GET['page']) ? intval($_GET['page']) : 0;
 $getPage = max($getPage, 1);
 $zPage = new zPage(1100, 10, 11, $getPage, '?page=', '&type=1');
 echo $zPage->html();