PHP实现适用于文件内容操作的分页类

<?php 
class strpage {
 private $current;  //当前页 
 private $file;  //操作文件
 private $totalpage;  //总的页数
 private $url;  //传递的参数
 private $pagelen;  //每页显示的长度
 
 function __construct( $file,$len = 200 ){
 $this->file = file_get_contents($file);
 $this->pagelen = $len;
 $this->current = isset($_get['page'])?$_get['page']:1;
 $this->totalpage = $this->gettotalpage();
 $this->url = $this->geturl();
 }
 
 
 //获取到这个文件总的长度
 private function gettotalpage(){
 return ceil(strlen($this->file)/$this->pagelen);
 }
 
 //获取当前传递的参数,保留参数，page参数动态变化
 private function geturl(){
 $url =parse_url($_server['request_uri']);
 parse_str($url['query'],$queryarr);
 unset($queryarr['page']);
 $querystr = http_build_query($queryarr);
 return $url['path'].'?'.$querystr.'&page='; 
 }
 
 
 //首页
 private function first(){
 if($this->current>1)
  return "<a href='".$this->url."1'>首页</a>";
 }
 //上一页
 private function pre(){
 if( $this->current > 1 )
  return "<a href='".$this->url.($this->current-1)."'>上一页</a>";
 }
 //下一页
 private function next(){
 if( $this->current < $this->totalpage)
  return "<a href='".$this->url.($this->current+1)."'>下一页</a>";
 }
 //最后一页
 private function end(){
 if( $this->current < $this->totalpage )
  return "<a href='".$this->url.$this->totalpage."'>末页</a>";
 }
 
 public function pagelist(){
 $pageliststr = '';
 for ($i=1;$i<=$this->totalpage;$i++){
  if($i==$this->current){
  $pageliststr.="<span style='font-size:20px;color:#f00'>".$i."</span> ";
  }else{
  $pageliststr.="<a href='".$this->url.$i."'>".$i." </a>";
  }
 }
 return $pageliststr;
 }
 
 public function pagestyle($style=1){
  switch ($style){
  case 1:
   return "共有".$this->totalpage."页".$this->first().$this->pre().$this->pagelist().$this->next().$this->end();
   break;
  case 2;
  return $this->pagelist();
  break;
  }
 }
 
 public function getcontents(){
 $prepagelen = strlen($this->substrs($this->current-1));
 $currentpagelen = strlen($this->substrs($this->current));
 return substr($this->file, $prepagelen,$currentpagelen-$prepagelen);
 }
 
 public function substrs($page){ 
  $string = '';
  $len= $page*$this->pagelen;
  for( $i=0; $i<$len; $i++ ){
   if( ord(substr($this->file,$i,1))>0xa0 ){
   $string .= substr($this->file,$i,3);
   $i = $i+2;
  }else{
   $string .= substr($this->file, $i,1);
  }
  }
  return $string;
  
 }
 
}