if($file_type!="image/jpeg" && $file_type!="image/pjpeg"){
        echo "文件类型只能是 jpg 格式";
        exit();
    }
    //判断上传是否 OK
    if(is_uploaded_file($_FILES['myfile']['tmp_name'])){
        //得到上传的文件 转存到你希望的目录
        $upload_file=$_FILES['myfile']['tmp_name'];
        
        //防止图片覆盖问题，为每个用户建立一个文件夹    
        $user_path=$_SERVER['DOCUMENT_ROOT']."/file/up/".$username;
        if(!file_exists($user_path)){
            mkdir ($user_path);
        }

        //$move_to_file=$user_path."/".$_FILES['myfile']['name'];
        //防止用户上传用户名相同的问题
        $file_true_name=$_FILES['myfile']['name'];
        $move_to_file=$user_path."/".time().rand(1,1000).substr($file_true_name,strripos($file_true
_name,"."));

        //echo $upload_file.$move_to_file;
        //中文要转码
        if(move_uploaded_file($upload_file,iconv("utf-8","gb2312","$move_to_file"))){
            echo $_FILES['myfile']['name']."上传成功";
        }else{
            echo "上传失败";
        }
    }else{
        echo "上传失败";
    }
?>
3、封装：
<?php
/**
* php 文件上传类
* by www.jbxue.com
*/
    class Upload{
        public $upload_name; //上传文件名
        public $upload_tmp_path; //上传文件保存到服务器的 temp 路径
        public $file_size;
        public $file_type;
        public $file_save_path;