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# PHP input/output streams

PHP 3.0.13 and up, `php://output` and `php://input` since PHP 4.3.0, `php://filter` since PHP 5.0.0

- `php://stdin`

- `php://stdout`

- `php://stderr`

- `php://output`

- `php://input`

- `php://filter`

`php://stdin`, `php://stdout` and `php://stderr` allow access to the corresponding input or output stream of the PHP process.

`php://output` allows you to write to the output buffer mechanism in the same way as print() and echo().

`php://input` allows you to read raw POST data. It is a less memory intensive alternative to $HTTP_RAW_POST_DATA and does not need any special `php.ini` directives.

`php://stdin` and `php://input` are read-only, whereas `php://stdout`, `php://stderr` and `php://output` are write-only.

`php://filter` is a kind of meta-wrapper designed to permit the application of filters to a stream at the time of opening. This is useful with all-in-one file functions such as readfile(), file(), and file_get_contents() where there is otherwise no opportunity to apply a filter to the stream prior the contents being read.

The `php://filter` target takes the following 'parameters' as parts of its 'path'.

- /resource=<stream to be filtered> (required) This parameter must be located at the end of your `php://filter` specification and should point to the stream which you want filtered.

  `<?php /* This is equivalent to simply: readfile("http://www.example.com"); since no filters are actually specified */ readfile("php://filter/resource=http://www.example.com"); ?>`

- /read=<filter list to apply to read chain> (optional) This parameter takes one or more filternames separated by the pipe character |.

  `<?php /* This will output the contents of www.example.com entirely in uppercase */ readfile("php://filter/read=string.toupper/resource=http://www.example.com"); /* This will do the same as above but will also ROT13 encode it */ readfile("php://filter/read=string.toupper|string.rot13/resource=http://www.example.com"); ?>`

- /write=<filter list to apply to write chain> (optional) This parameter takes one or more filternames separated by the pipe character |.

  `<?php /* This will filter the string "Hello World" through the rot13 filter, then write to example.txt in the current directory */ file_set_contents("php://filter/write=string.rot13/resource=example.txt","Hello World"); ?>`

- /<filter list to apply to both chains> (optional) Any filter lists which are not prefixed specifically by read= or write= will be applied to both the read and write chains (as appropriate).

表格 L-6. Wrapper Summary (For php://filter, refer to summary of wrapper being filtered.)

Attribute | Supported
--- | ---
Restricted by allow_url_fopen. | No
Allows Reading | php://stdin and php://input only.
Allows Writing | php://stdout, php://stderr, and php://output only.
Allows Appending | php://stdout, php://stderr, and php://output only. (Equivalent to writing)
Allows Simultaneous Reading and Writing | No. These wrappers are unidirectional.
Supports stat() | No
Supports unlink() | No
Supports rename() | No
Supports mkdir() | No
Supports rmdir() | No

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