php 上传图片自动生成缩略图

<form action="uploads.php" method="post" enctype="multipart/form-data">
 <input type='file' name='image'><br>
 <input type='submit' name='sub' value='提交'>
</form>

uploads.php文件

<?php
class image_upload{
 private $srcimg;  //原图片
 private $destimg;  // 目标图片
 private $width;   //原图片的宽度
 private $height;  //原图片的高度
 private $type;   //原文件的图片类型
 private $thumb_width;  //缩略图的宽度
 private $thumb_height; //缩略图的高度
 private $cut;   //是否剪切图片到指定高度
 private $tmp;   //上传图片的临时地址
 private $error;
 private $im;   // 创建一个临时的图片句柄
 private $new_name;  //上传文件的新名字
 
 function __construct($srcimg,$t_width,$t_height,$cut,$tmp,$error){
  $this->srcimg=$srcimg;
  $this->thumb_width=$t_width;
  $this->thumb_height=$t_height;
  $this->cut=$cut;
  $this->tmp=$tmp;
  $this->error=$error;
  $this->get_srcimg_type();
  $this->get_new_upload_name();
  

   }
  
 function img_upload(){
  //文件上传的方法 
  $this->check_error($this->error);
  $this->in_type();
  $dst_dir='./images';
  if(!is_dir($dst_dir)){
   mkdir($dst_dir);
   echo "%%%<BR>";
  }
  
  if(is_uploaded_file($this->tmp)){
   if(move_uploaded_file($this->tmp, $this->new_name)){
    echo "文件上传成功<br>";
    return true;
   }else{
    echo '文件不能被移动，上传失败';
    exit;
   }
  }else{
    echo '文件上传可能被攻击';
    exit;
  }
  
 }
 
 function make_thumbnail(){
  //生成缩略图的方法
  $this->get_dest_imgpath();
  $this->make_im();
  $this->width=imagesx($this->im);
  $this->height=imagesy($this->im);
  
  $thumb_ratio=$this->thumb_width/$this->thumb_height;
  $ratio=$this->width/$this->height;
  
  
  if($this->cut==1){  //是否裁剪
    if($ratio>=$thumb_ratio){
     $img=imagecreatetruecolor($this->thumb_width, $this->thumb_height);
     imagecopyresampled($img, $this->im, 0, 0, 0, 0, $this->thumb_width, $this->thumb_height, $this->height*$thumb_ratio, $this->height);
     imagejpeg($img,$this->destimg);       
     echo "缩略图生成成功";
    }else{
     $img=imagecreatetruecolor($this->thumb_width, $this->thumb_height);
     imagecopyresampled($img, $this->im, 0, 0, 0, 0, $this->thumb_width, $this->thumb_height, $this->width, $this->width/$thumb_ratio);
     imagejpeg($img,$this->destimg);       
     echo "缩略图生成成功";  
    }
  }else{
   if($ratio>=$thumb_ratio){
     $img=imagecreatetruecolor($this->thumb_height*$thumb_ratio, $this->thumb_height);
     imagecopyresampled($img, $this->im, 0, 0, 0, 0, $this->thumb_height*$thumb_ratio, $this->thumb_height, $this->width, $this->height);
     imagejpeg($img,$this->destimg);       
     echo "缩略图生成成功";
   }else{
     $img=imagecreatetruecolor($this->thumb_width, $this->thumb_width/$thumb_ratio);
     imagecopyresampled($img, $this->im, 0, 0, 0, 0, $this->thumb_width, $this->thumb_width/$thumb_ratio, $this->width, $this->height);
     imagejpeg($img,$this->destimg);       
     echo "缩略图生成成功";
   }
  }
  imagedestroy($this->im);
  imagedestroy($img);
 }
 
 private function check_error($error){
  //检查文件上传传得错误；
  if($error>0){
   switch($error){
    case 1:
     echo "上传文件的大小超过了PHP.INI文件中得配置<br>";
     break;
    case 2:
     echo "上传文件的大小超过了表单中的限制大小<br>";
     break;
    case 3:
     echo "只有部分文件被上传<br>";
     break;
    case 4:
     echo "没有文件被上传<br>";
     break;
    case 6:
     echo "php.ini中没有设置图片存放的临时未知<br>";
     break;
    case 7:
     echo "硬盘不可以写入，上传失败<br>";
     break;
    default:
     echo "未知错误";
     break;
   }
  }
 }
 
 private function get_srcimg_type(){
  //判断源文件的图片类型
  $this->type=substr(strrchr($this->srcimg, '.'),'1');
 }
 
 private function in_type(){
  //检查文件是否符合类型
  $type_arr=array('gif','jpg','png');
  if(!in_array($this->type, $type_arr)){
   echo "只支持PNG,GIF,JPG 三种类型的文件格式……，请重新上传正确的格式";
   exit;
  }
 }
 
 private function get_new_upload_name(){
  //上传的文件生成新的名字
  $this->new_name='images/'.date('YmdHis').'.'.$this->type;
 
 }
 private function make_im(){
  //从原文件新建一幅图像
  switch($this->type){
   case 'jpg':
    $this->im=imagecreatefromjpeg($this->new_name);
    break;
   case 'gif':
    $this->im=imagecreatefromgif($this->new_name);
    break;
   case 'png':
    $this->im=imagecreatefrompng($this->new_name);
    break;
   } 
 }
 private function  get_dest_imgpath(){
  //得到缩略图的存储路径
  $len1=strlen($this->new_name);
  $len2=strlen(strrchr($this->new_name,'.'));
  $len3=$len1-$len2;
  $this->destimg=substr($this->new_name,0,$len3).'_small.'.$this->type;
 }
 
}
 print_r($_FILES);
 $file=$_FILES['image'];
echo $file['name'];
 $uploads=new image_upload($file['name'], 120, 160, 1,  $file['tmp_name'],$file['error'] );
  if($uploads->img_upload()){
   $uploads->make_thumbnail();
  }
 
?>