Detailed explanation of filter protocol in PHP

This article mainly shares with you the detailed explanation of the filter protocol in PHP, hoping to help everyone.

php:// — 访问各个输入/输出流（I/O streams）php://input 是个可以访问请求的原始数据的只读流。
php://filter 是一种设计用来允许过滤器程序在打开时成为流的封装协议。这对于单独具有完整功能的文件函数非常有用，否则就没有机会在读取内容之前将过滤器应用于流之上。
该协议语法为：php://filter:/<action>=<name>
比如 php://filter:/resource=http://www.baidu.com

Use php://filter to obtain web page content:

<?php$url = 'http://www.phpfamily.cn';$data = file_get_contents('php://filter/resource=' . $url);
echo $data;  //输出结果我http://www.phpfamily.cn页面的内容

Parameter list of php://filter

##ParameterFunctionreadReadwriteWriteresourceData source##read parameter value can be

string.strip_tags: Clear all html tags in the data stream

string.toupper: Convert the content in the data stream to uppercase

string.tolower: Convert the content in the data stream to lowercase
convert. base64-encode: Convert the content in the data stream to base64 encoding convert.base64-decode: The corresponding decoding
above is a typical file inclusion vulnerability. We can view the code we want to see by constructing a statement containing the vulnerability: file=php://filter/convert.base64-encode/resource=index.php. Then decode the resulting base64 code.

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