<?php
/核心:首页、上一页、下一页、尾页的url/
/超全局$_SERVER/
$page = new Page(5,60);
var_dump($page->allUrl());
class Page{
// 每页显示的个数
protected $number;
// 一共有多少数据
protected $totalCount;
// 当前页
protected $page;
// url
protected $url;

public function __construct($number,$totalCount){
$this->number= $number;
$this->totalCount = $totalCount;
//得到总页数
$this->totalPage = $this->getTotalPage();
//得到当前页数
$this->page = $this->getPage();
//得到URL
$this->url = $this->getUrl();
echo $this->url;
}
/得到总页数并向上取整/
protected function getTotalPage(){
return ceil($this->totalCount/$this->number);
}
/*/
protected function getPage(){
if (empty($_GET['page'])){
$page=1;
}elseif ($_GET['page'] > $this->totalPage){
$page = $this->totalPage;
}elseif ($_GET["page"]<1){
$page = 1;
}else{
$page = $_GET['page'];
}
return $page;
}
protected function getUrl(){
//得到协议名
$scheme = $_SERVER['REQUEST_SCHEME'];
//得到主机名
$host= $_SERVER['SERVER_NAME'];
//得到端口号
$port = $_SERVER['SERVER_PORT'];
//得到路径和请求字符串
$url = $_SERVER['REQUEST_URI'];
/中间做处理,要将page=5等这种字符串拼接URL
中，所以如果原来的url中有page这个参数，我们首先
需要将原来的page参数给清空*/
$urlArray = parse_url($url);
// var_dump($urlArray);

$path = $urlArray['path'];
if (!empty($urlArray['query'])){
  //将query中的值转化为数组
  parse_str($urlArray['query'],$array);
  //如果他有page就将它删掉
  unset($array['page']);
  //将关联数组转化为query
  $query = http_build_query($array);
  //不为空的话就与path连结
  if ($query != ''){
    $path = $path.'?'.$query;
  }
}
return 'http://'. $host.':'.$port.$path;

}
protected function setUrl($str){
if (strstr($this->url,'?')){
$url = $this->url.'&'.$str;
}else{
$url = $this->url.'?'.$str;
}
return $url;
}
/所有的url/
public function allUrl(){
return [
'first' => $this->first(),'next' => $this->next(),'prev'=> $this->prev(),'end'=> $this->end(),];
}
/首页/
public function first(){
return $this->setUrl('page=1');
}
/下一页/
public function next(){
//根据当前page得带下一页的页码
if ($this->page+1 > $this->totalPage) {
$page = $this->totalPage;
}else{
$page = $this->page+1;
}
return $this->setUrl('page='.$page);
}
/上一页/
public function prev(){
//根据当前page得带下一页的页码
if ($this->page - 1 < 1) {
$page = 1;
}else{
$page = $this->page-1;
}
return $this->setUrl('page='.$page);
}
/尾页/
public function end(){
return $this->setUrl('page='.$this->totalPage);
}
/limit 0,5/
public function limit(){
$offset = ($this->page-1)*$this->number;
return $offset.','.$this->number;
}

}