PHP下载远程文件

<?phpif (@$_GET['xfer']) {$uurl = trim($_POST['from']);$durl = trim($_POST['to']);if(!$uurl){echo "请输入下载的文件地址";exit;}if(!$durl){echo "请输入保存的文件地址";exit;}if(!file_exists($durl)){echo "请输入正确的下载地址";exit;}$file = file_get_contents($uurl);if(!$file == ""){@file_put_contents($durl,$file) or die("下载失败");$size = round((filesize($durl)/1000000), 3);echo  "下载成功<br>";?><a href="<?php echo $uurl ?>"><?php echo $uurl; ?></a><br><a href="<?php echo $durl ?>"><?php echo $durl; ?></a> : <?php echo $size; ?> MB<?php} else {echo "获取文件失败";}} else {?><form action="<?php $PHP_SELF ?>?xfer=true" method="post">from(http://): <input type="text" name="from"><br>to(filename): <input type="text" name="to"><br><input type="submit" value="transload"></form><?php}?>