PHP分页原理

<?php
class page{
	public $pageSize;		//每页记录数
	public $rsTotal;		//总记录数
	public $pageTotal;
	public $nowpage;		//当前页			
	public $offset;			//limit偏移量：limit 0,20
	public $url;
	public $prePage = 'page';
	public $pageInfo;
	public $pageHtml;		//分页连接:首页 上一页 下一页 末页

	function __construct($pageSize=20,$rsTotal){
		$this->pageSize	= $pageSize;
		$this->rsTotal		= $rsTotal;
		$this->pageTotal	= ceil($rsTotal/$pageSize);
		$this->nowPage		= $this->getNowPage();
		$this->offset		= $this->getOffset();
		$this->url			= $this->getUrl();
		$this->pageInfo	= $this->pageInfo();
		$this->pageHtml	= $this->pageHtml($this->pageInfo);
	}

	//获取当前页码
	private function getNowPage(){
		$nowPage = isset($_GET[$this->prePage])?$this->f_Get($this->prePage):1;
		$nowPage = $nowPage<1 ? 1 : $nowPage;
		$nowPage = $nowPage>$this->pageTotal ? $this->pageTotal : $nowPage;
		return $nowPage;
	}

	//获取当前页的记录偏移量、
	private function getOffset(){
		$offset = " limit ".($this->nowPage-1)*$this->pageSize.",".$this->pageSize;
		return $offset;
	}

	//生成翻页html代码
	public function pageHtml($pageInfo){
		//首页
		if(!empty($pageInfo['first'])){
			if($this->nowPage=="" || $this->nowPage==1){
				$pageHtml = '<span class="page_first">'.$pageInfo['first'].'</span>';
			}else{
				$pageHtml = '<span class="page_first"><a href="?'.$this->url['first'].'">'.$pageInfo['first'].'</a></span>';
			}
		}
		//上一页
		if(!empty($pageInfo['pre'])){
			if($this->nowPage=="" || $this->nowPage==1){
				$pageHtml .= '<span class="page_pre">'.$pageInfo['pre'].'</span>';
			}else{
				$pageHtml .= '<span class="page_pre"><a href="?'.$this->url['pre'].'">'.$pageInfo['pre'].'</a></span>';
			}
		}

		//下一页
		if(!empty($pageInfo['next'])){
			if($this->nowPage >= $this->pageTotal){
				$pageHtml .= '<span class="page_next">'.$pageInfo['next'].'</span>';
			}else{
				$pageHtml .= '<span class="page_next"><a href="?'.$this->url['next'].'">'.$pageInfo['next'].'</a></span>';
			}
		}

		//末页
		if(!empty($pageInfo['last'])){
			if($this->nowPage >= $this->pageTotal){
				$pageHtml .= '<span class="page_last">'.$pageInfo['last'].'</span>';
			}else{
				$pageHtml .= '<span class="page_last"><a href="?'.$this->url['last'].'">'.$pageInfo['last'].'</a></span>';
			}
		}

		if(!empty($pageInfo['t_page'])){
			$pageHtml .= '<span class="t_page">'.str_replace("%i%",$this->pageTotal,$pageInfo['t_page']).'</span>';
		}
		if(!empty($pageInfo['nowPage'])){
			$pageHtml .= '<span class="now_page">'.str_replace("%i%",$this->nowPage,$pageInfo['nowPage']).'</span>';
		}
		if(!empty($pageInfo['r_total'])){
			$pageHtml .= '<span class="r_page">'.str_replace("%i%",$this->rsTotal,$pageInfo['r_total']).'</span>';
		}
		
		return $pageHtml;
	}

	//获取当前URL
	private function getUrl(){
		$str = '';
		$urlStr = $_GET;
		$queryString = array();
		foreach($urlStr as $key=>$value){
			if($key == $this->prePage){
				continue;
			}
			$str = $key."=".$value."&";
		}
		$nextTmp	= $this->nowPage+1;
		$preTmp		= $this->nowPage-1;
		$last		= $str.$this->prePage.'='.$this->pageTotal;
		$next		= $str.$this->prePage.'='.$nextTmp;
		$pre		= $str.$this->prePage.'='.$preTmp;
		$first		= $str.$this->prePage.'=1';

		$queryString = array("pre"=>$pre,"next"=>$next,"last"=>$last,"first"=>$first);
		return $queryString;
	}

	private function pageInfo(){
		return array("first"=>"首页","last"=>"末页","next"=>"下一页","pre"=>"上一页","t_page"=>"共 %i% 页","nowPage"=>"当前第 %i% 页","r_toal"=>"共 %i% 条");
	}

	//过滤函数
	private function f_Get($GET){
		$GET = $_GET[$GET];
		return preg_replace("/[^0-9]/i","",$GET);
	}
}
$page=new Page(20,100);
echo $page->pageHtml;
?>