PHP 远程图片获取到本地

<?php 
/*
 * 远程图片获取到本地
 */
function GrabImage($url){
	if($url != ""){	//如果图片地址为空
		$ext = strrchr($url,".");	//判断图片的格式
		if($ext != ".jpg" && $ext != ".gif" && $ext != "$png"){
			return false;exit;
		}
		$filename_r = time().rand(10,9000).$ext;	//给图片命名
		$filename = "getimg/".$filename_r;
		ob_start();	//打开缓冲区
		readfile($url);	
		$imginfo = ob_get_contents();	//获得缓冲区的内容
		ob_end_clean(); //清除并关闭缓冲区
		$fp = fopen($filename,"a");	
		fwrite($fp,$imginfo);
		fclose($fp);
	}else{
		return false;
	}
}
$start_time = microtime(true);
GrabImage("http://img4.shougongke.com/Public/advance/53846840dafb4.jpg");
$end_time = microtime(true);
$time = round($end_time-$start_time,3);
echo "程序总共用时".$time."秒";
?>