php上传文件基础

<?php
 /*****************************************
   Title :文件上传详解
   Author:leehui1983(辉老大)
   Finish Date  :2006-12-28
  *****************************************/
   $uploaddir = "./files/";//设置文件保存目录 注意包含/
   $type=array("jpg","gif","bmp","jpeg","png");//设置允许上传文件的类型
   $patch="http://127.0.0.1/cr_downloadphp/upload/files/";//程序所在路径   

   //获取文件后缀名函数
      function fileext($filename)
    {
        return substr(strrchr($filename, ‘.‘), 1);
    }
   //生成随机文件名函数
    function random($length)
    {
        $hash = ‘CR-‘;
        $chars = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz‘;
        $max = strlen($chars) - 1;
        mt_srand((double)microtime() * 1000000);
            for($i = 0; $i < $length; $i++)
            {
                $hash .= $chars[mt_rand(0, $max)];
            }
        return $hash;
    }
   $a=strtolower(fileext($_FILES[‘file‘][‘name‘]));
   //判断文件类型
   if(!in_array(strtolower(fileext($_FILES[‘file‘][‘name‘])),$type))
     {
        $text=implode(",",$type);
        echo "您只能上传以下类型文件: ",$text,"<br>";
     }
   //生成目标文件的文件名
   else{
    $filename=explode(".",$_FILES[‘file‘][‘name‘]);
        do
        {
            $filename[0]=random(10); //设置随机数长度
            $name=implode(".",$filename);
            //$name1=$name.".Mcncc";
            $uploadfile=$uploaddir.$name;
        }
   while(file_exists($uploadfile));
        if (move_uploaded_file($_FILES[‘file‘][‘tmp_name‘],$uploadfile)){   

            if(is_uploaded_file($_FILES[‘file‘][‘tmp_name‘])){
                //输出图片预览
                echo "<center>您的文件已经上传完毕 上传图片预览: </center><br><center><img src=‘$uploadfile‘></center>";
                echo"<br><center><a href=‘javascript:history.go(-1)‘>继续上传</a></center>";
              }
              else{
                echo "上传失败！";
              }
        }
   }
?>