用PHP、js判断文件类型

1.用JAVASCRIPT判断文件后缀，给form加上onsubmit=”return chk()”

JavaScript代码
<script language=”javascript”>    
<!–   
function chk () {    

Ary = form1.userfile.value.split(‘.’);    
filetype=Ary[Ary.length-1];    
if (filetype!=’txt’)    
{    
alert (‘请把文件转换成.txt格式’);    
return false;    
}    
}    
–>   
</script> 
2.用PHP判断文件后缀
PHP代码
if(isset($_FILES['upload']))        //***判断图象类型   
   if($_FILES['upload']['type']==”image/pjpeg”||$_FILES['upload']['typle']==”image/gif”)   
      {   
       $type=strcmp($_FILES['upload']['type'],”image/pjpeg”)==0?”jpg”:”gif”;   
           if($_FILES['upload']['size']/1024<=20&$_FILES['upload']['error']==UPLOAD_ERR_OK)//判断图象大小   
         
            {   
              $filename=md5(uniqid(rand())).”.”.$type;   
              $move=move_uploaded_file($_FILES['upload']['tmp_name'],”image/$filename”);   
             }   
           else  
             {   
              echo “error!The picture is larger than 20k”;   
             exit();   
             }   
         }   
   else  
     {   
      echo “the file type wrong!”;   
          exit();   
     }

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