Simple PHP file upload class for beginners, _PHP tutorial

<&#63;php
class Test_Upload{
 
  protected $_uploaded = array();
  protected $_destination;  
  protected $_max = 1024000;
  protected $_messages = array();
  protected $_permited = array(
                'image/gif',
                'image/jpeg',
                'image/pjpeg',
                'image/png'  
  );
  protected $_renamed = false;
   
  /**
   * 
   * @param mix $path
   * 
   */
  public function __construct($path){
     
    if (!is_dir($path) || !is_writable($path)){
      throw new Exception("文件名不可写，或者不是目录！");
    }
    $this->_destination = $path;
    $this->_uploaded = $_FILES;
  }
  /**
   * 移动文件
   * 
   */
  public function move(){
     
    $filed = current($this->_uploaded); 
       
    $isOk = $this->checkError($filed['name'], $filed['error']);
    //debug ok
    if ($isOk){
      $sizeOk = $this->checkSize($filed['name'], $filed['size']);
      $typeOk = $this->checkType($filed['name'], $filed['type']);
      if ($sizeOk && $typeOk){
         
        $success = move_uploaded_file($filed['tmp_name'], $this->_destination.$filed['name']);
         
        if ($success){
          $this->_messages[] = $filed['name']."文件上传成功";
        }else {
          $this->_messages[] = $filed['name']."文件上传失败";
        }
      }
       
    }
  }
  /**
   * 查询messages数组内容 
   *
   */
  public function getMessages(){
    return $this->_messages;
  }
   
  /**
   * 检测上传的文件大小
   * @param mix $string
   * @param int $size
   */
  public function checkSize($filename, $size){
     
    if ($size == 0){
      return false;
    }else if ($size > $this->_max){
      $this->_messages[] = "文件超出上传限制大小".$this->getMaxsize();
      return false;
    }else { 
      return true;
    }
  }
   
  /**
   * 检测上传文件的类型
   * @param mix $filename
   * @param mix $type
   */
  protected function checkType($filename, $type){
    if (!in_array($type, $this->_permited)){
      $this->_messages[] = "该文件类型是不被允许的上传类型";
      return false;
    }else {
      return true;
    }
  }
   
  /**
   * 获取文件大小
   * 
   */
  public function getMaxsize(){
    return number_format($this->_max / 1024, 1).'KB';
  }
   
  /**
   * 检测上传错误
   * @param mix $filename
   * @param int $error
   * 
   */
  public function checkError($filename, $error){
    switch ($error){
      case 0 : return true;
      case 1 :
      case 2 : $this->_messages[] = "文件过大！"; return true;
      case 3 : $this->_messages[] = "错误上传文件！";return false;
      case 4 : $this->_messages[] = "没有选择文件!"; return false;
      default : $this->_messages[] = "系统错误!"; return false;
    }
  }
}
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