uploader 上传服务器返回500错误

uploader 上传服务器返回500错误

服务端代码

  if ($_SERVER['REQUEST_METHOD'] == 'POST')   
        {  
            $ret=array('strings'=>$_POST,'error'=>'0');  
            $fs=array();  
            foreach ( $_FILES as $name=>$file ) {  

                $fn=$file['name'];  
                $ft=strrpos($fn,'.',0);  
                $fm=substr($fn,0,$ft);  
                $fe=substr($fn,$ft);  
                $fp='files/'.$fn;  
                $fi=1;  
                while( file_exists($fp) ) {  
                    $fn=$fm.'['.$fi.']'.$fe;  
                    $fp='files/'.$fn;  
                    $fi++;  
                }  
                move_uploaded_file($file['tmp_name'],$fp);  
                $fs[$name]=array('name'=>$fn,'url'=>$fp,'type'=>$file['type'],'size'=>$file['size'],);  
            }  
            $ret['files']=$fs;        
            echo json_encode($ret);  
        }else{  
            echo "{'error':'Unsupport GET request!'}";  
        }