Detailed explanation of php paging class examples

<?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[&#39;page&#39;])){
      $page=1;
    }elseif ($_GET[&#39;page&#39;] > $this->totalPage){
      $page = $this->totalPage;
    }elseif ($_GET["page"]<1){
      $page = 1;
    }else{
      $page = $_GET[&#39;page&#39;];
    }
    return $page;
  }
  protected function getUrl(){
    //得到协议名
    $scheme = $_SERVER[&#39;REQUEST_SCHEME&#39;];
    //得到主机名
    $host= $_SERVER[&#39;SERVER_NAME&#39;];
    //得到端口号
    $port = $_SERVER[&#39;SERVER_PORT&#39;];
    //得到路径和请求字符串
    $url = $_SERVER[&#39;REQUEST_URI&#39;];
    /*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 = $urlArray[&#39;path&#39;];
    if (!empty($urlArray[&#39;query&#39;])){
      //将query中的值转化为数组
      parse_str($urlArray[&#39;query&#39;],$array);
      //如果他有page就将它删掉
      unset($array[&#39;page&#39;]);
      //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 != &#39;&#39;){
        $path = $path.&#39;?&#39;.$query;
      }
    }
    return &#39;http://&#39;. $host.&#39;:&#39;.$port.$path;
  }
  protected function setUrl($str){
    if (strstr($this->url, &#39;?&#39;)){
      $url = $this->url.&#39;&&#39;.$str;
    }else{
      $url = $this->url.&#39;?&#39;.$str;
    }
    return $url;
  }
  /*所有的url*/
  public function allUrl(){
    return [
      &#39;first&#39; => $this->first(),
      &#39;next&#39; => $this->next(),
      &#39;prev&#39;=> $this->prev(),
      &#39;end&#39;=> $this->end(),
    ];
  }
  /*首页*/
  public function first(){
    return $this->setUrl(&#39;page=1&#39;);
  }
  /*下一页*/
  public function next(){
    //根据当前page得带下一页的页码
    if ($this->page+1 > $this->totalPage) {
      $page = $this->totalPage;
    }else{
      $page = $this->page+1;
    }
    return $this->setUrl(&#39;page=&#39;.$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 $this->setUrl(&#39;page=&#39;.$page);
  }
  /*尾页*/
  public function end(){
    return $this->setUrl(&#39;page=&#39;.$this->totalPage);
  }
  /*limit 0,5*/
  public function limit(){
    $offset = ($this->page-1)*$this->number;
    return $offset.&#39;,&#39;.$this->number;
  }
  
}