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 : intval@163.com
 * 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();