<?php
/*核心:首頁、上一頁、下一頁、尾頁的url*/
/*超全局$_SERVER*/
$page = new Page(5,60);
var_dump($page->allUrl());
class Page{
//   每頁顯示的個數
  protected $number;
//   一共有多少數據
  protected $totalCount;
//   當前頁
  protected $page;
//   url
  protected $url;
  
  public function __construct($number,$totalCount){
    $this->number= $number;
    $this->totalCount = $totalCount;
    //得到總頁數
    $this->totalPage = $this->getTotalPage();
    //得到當前頁數
    $this->page = $this->getPage();
    //得到URL
    $this->url = $this->getUrl();
    echo $this->url;
  }
  /*得到總頁數并向上取整*/
  protected function getTotalPage(){
    return   ceil($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(){
    //得到協議名
    $scheme = $_SERVER['REQUEST_SCHEME'];
    //得到主機名
    $host= $_SERVER['SERVER_NAME'];
    //得到端口號
    $port = $_SERVER['SERVER_PORT'];
    //得到路徑和請求字符串
    $url = $_SERVER['REQUEST_URI'];
    /*中間做處理,要將page=5等這種字符串拼接URL
    中，所以如果原來的url中有page這個參數，我們首先
    需要將原來的page參數給清空*/
    $urlArray = parse_url($url);
//     var_dump($urlArray);

    $path = $urlArray['path'];
    if (!empty($urlArray['query'])){
      //將query中的值轉化為數組
      parse_str($urlArray['query'],$array);
      //如果他有page就將它刪掉
      unset($array['page']);
      //將關聯數組轉化為query
      $query = http_build_query($array);
      //不為空的話就與path連結
      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(),
    ];
  }
  /*首頁*/
  public function first(){
    return $this->setUrl('page=1');
  }
  /*下一頁*/
  public function next(){
    //根據當前page得帶下一頁的頁碼
    if ($this->page+1 > $this->totalPage) {
      $page = $this->totalPage;
    }else{
      $page = $this->page+1;
    }
    return $this->setUrl('page='.$page);
  }
  /*上一頁*/
  public function prev(){
    //根據當前page得帶下一頁的頁碼
    if ($this->page - 1 < 1) {
      $page = 1;
    }else{
      $page = $this->page-1;
    }
    return $this->setUrl('page='.$page);
  }
  /*尾頁*/
  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;
  }
  
}