根据图片的url，获取远程图片，利用curl进行图片的下载，并进行存储，最后返回图片的相关保存信息。
function getimage($url,$save_dir='',$filename='',$type=0){
            if(trim($url)==''){
                return array('file_name'=>'','save_path'=>'','error'=>1);
            }
            if(trim($save_dir)==''){
                $save_dir='./';
            }
            if(trim($filename)==''){//保存文件名
                $ext=strrchr($url,'.');
            if($ext!='.gif'&&$ext!='.jpg'&&$ext!='.png'&&$ext!='.jpeg'){
                return array('file_name'=>'','save_path'=>'','error'=>3);
            }
                $filename=time().rand(0,10000).$ext;
            }
            if(0!==strrpos($save_dir,'/')){
                $save_dir.='/';
            }
            //创建保存目录
            if(!file_exists($save_dir)&&!mkdir($save_dir,0777,true)){
                return array('file_name'=>'','save_path'=>'','error'=>5);
            }
            //获取远程文件所采用的方法
            if($type){
                $ch=curl_init();
                $timeout=5;
                curl_setopt($ch,curlopt_url,$url);
                curl_setopt($ch,curlopt_returntransfer,1);
                curl_setopt($ch,curlopt_connecttimeout,$timeout);
                $img=curl_exec($ch);
                curl_close($ch);
            }else{
                ob_start();
                readfile($url);
                $img=ob_get_contents();
                ob_end_clean();
            }
            //$size=strlen($img);
            //文件大小
            $fp2=@fopen($save_dir.$filename,'a');
            fwrite($fp2,$img);
            fclose($fp2);
            unset($img,$url);
            return array('file_name'=>$filename,'save_path'=>$save_dir.$filename,'error'=>0);
        }
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