Implement file download using PHP

 Here I wrote a program on how to use PHP to download files, mainly for the convenience of my own search, and also for the convenience of everyone to check and study (of course there are other similar codes on the Internet). For detailed analysis, see the original program comments.

PHP implementation file download program:

FileDownService.class.php

<?php
	//封装到类
	class FileDownService {
		//下载文件的函数

		//对函数的说明
		//参数说明 $file_name 文件名
		//         $file_sub_dir 下载文件的子路径 "/xxx/xxx/"
		function down_file($file_name, $file_sub_dir) {
			//如果文件是中文的
			//原因 php文件函数，比较古老，需要对中文转码 gb2312
			$file_name=iconv("utf-8","gb2312", $file_name);

			//使用绝对路径
			$file_path=$_SERVER[&#39;DOCUMENT_ROOT&#39;].$file_sub_dir.$file_name;

			//1.判断文件是否存在
			if(!file_exists($file_path)) {
				echo &#39;文件不存在!&#39;;
				return;
			}

			//2.打开文件
			$fp=fopen($file_path, "r");

			//3.获取下载文件的大小
			$file_size=filesize($file_path);

			//限制下载文件的大小
			/*if($file_size>10*1024*1024) {
				echo "<script language=&#39;javascript&#39;>window.alert('文件过大')</script>";
				return ;
			}*/

			//4.添加http的响应信息
			//返回的是文件
			header("Content-type: application/octet-stream");
			//按照字节大小返回
			header("Accept-Ranges: bytes");
			//返回文件大小
			header("Accept-Length: ".$file_size);
			//这里客户端的弹出对话框，对应的文件名
			header("Content-Disposition: attachment; filename=".$file_name);

			//5.向客户端回送数据
			$buffer=1024;

			//为了下载的安全，我们最好做一个文件字节读取计数器
			$file_count=0;
			//这句话用于判断文件是否结束
			while(!feof($fp) && $file_size-$file_count>0) {
				$file_data=fread($fp, $buffer);
				//统计读了多少个字节
				$file_count+=$buffer;
				//把部分数据回送给浏览器
				echo $file_data;
			}

			//6.关闭文件
			fclose($fp);
		}
	}
?>

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The above introduces the use of PHP to implement file downloading, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.