Basic knowledge of streams in PHP

This article mainly introduces the basic knowledge of PHP streams. Interested friends can refer to it. I hope it will be helpful to everyone.

Overview

Streams are a feature introduced in PHP 4.3, mainly to unify the working methods of files, sockets and other similar resources. PHP 4.3 has been around for a long time, but many programmers seem to be unable to use streams in PHP correctly, including me of course. I have encountered the use of streams in some programs before, such as php://input, but I have never had a chance to sort it out. Today I will sort out this part of the knowledge.

Stream is a resource provided by PHP, which can be used transparently by us, and stream is a very powerful tool. Proper use of streams in programs can take our programs to a new level.

Each stream implements a wrapper, which contains some additional code to handle special protocols and encodings. PHP provides some built-in wrappers, and we can also easily create and register custom wrappers. We can even use contexts and filters to alter and enhance wrappers.

Basic knowledge of streams

The form of streams in PHP is: ://. is the name of the wrapper, and the content of depends on the different wrapper syntax.
The default wrapper is file://, which means that the stream is used every time we access the file system. For example, we can use the following two methods to read files: readfile('/path/to/somefile.txt') and readfile('file:///path/to/somefile.txt'). Use these two method to read the file, you can get the same result.

As mentioned earlier, PHP provides some built-in wrappers, protocols and filters. To check which wrappers are installed on our machine, you can use the following functions:

The code is as follows:

<?php
    var_dump(stream_get_transports());
    var_dump(stream_get_wrappers());
    var_dump(stream_get_filters());
?>

The output content of my local environment is as follows:

The code is as follows :

array (size=8)
  0 => string 'tcp' (length=3)
  1 => string 'udp' (length=3)
  2 => string 'unix' (length=4)
  3 => string 'udg' (length=3)
  4 => string 'ssl' (length=3)
  5 => string 'sslv3' (length=5)
  6 => string 'sslv2' (length=5)
  7 => string 'tls' (length=3)
array (size=12)
  0 => string 'https' (length=5)
  1 => string 'ftps' (length=4)
  2 => string 'compress.zlib' (length=13)
  3 => string 'compress.bzip2' (length=14)
  4 => string 'php' (length=3)
  5 => string 'file' (length=4)
  6 => string 'glob' (length=4)
  7 => string 'data' (length=4)
  8 => string 'http' (length=4)
  9 => string 'ftp' (length=3)
  10 => string 'phar' (length=4)
  11 => string 'zip' (length=3)
array (size=12)
  0 => string 'zlib.*' (length=6)
  1 => string 'bzip2.*' (length=7)
  2 => string 'convert.iconv.*' (length=15)
  3 => string 'string.rot13' (length=12)
  4 => string 'string.toupper' (length=14)
  5 => string 'string.tolower' (length=14)
  6 => string 'string.strip_tags' (length=17)
  7 => string 'convert.*' (length=9)
  8 => string 'consumed' (length=8)
  9 => string 'dechunk' (length=7)
  10 => string 'mcrypt.*' (length=8)
  11 => string 'mdecrypt.*' (length=10)

In addition, we can customize or use third-party streams.

php://wrapper

PHP has its own wrapper for accessing input/output (I/O) streams. PHP has basic php://stdin, php://stdout, php://stderr wrappers corresponding to the default I/O resources. There is also a php://input stream, which is a read-only stream, and the content of the stream is the data requested by the post. This stream is especially useful when we put data in the body of a post request to request a remote service.

Because php://input is the most commonly used stream, here are some knowledge points:

1.php://input can read unprocessed POST data. Compared to $HTTP_RAW_POST_DATA, it puts less pressure on memory and does not require special php.ini settings. php://input cannot be used for enctype=multipart/form-data
2. Only when Content-Type is application/x-www-form-urlencoded and the submission method is POST method, $_POST data is the same as php:/ /Input data is "consistent" (with quotation marks, indicating that their formats are inconsistent and their content is consistent). In other cases, they are inconsistent
3.php://input cannot read GET data. This is because the _GET data is written as query_path in the PATH field of the http request header (header), rather than in the body part of the http request.

Stream Contexts

This part of the content has almost never been encountered in programming, and it is difficult for me to research it. If you are interested, you can Baidu it yourself .

Summary

Streams are not used much in daily programming. When using xml-rpc, the server side obtains client data, mainly through php Input stream input, this is a common scenario. Hackers may also use this part of the content when they invade the website.

Related recommendations:

How to use the Snoopy class to parse html files

php for file operations and characters String encryption method

php string operation method

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