$ cat test.php 

$ arc lint test.php 
>>> Lint for test.php:


   Warning  (PHPCS.W.Internal.NoCodeFound) 
    No PHP code was found in this file and short open tags are not allowed by
    this install of PHP. This file may be using short open tags but PHP does
    not allow them.

    >>>        1

public function supportsReadDataFromStdin() {
  return true;
}

$ vendor/bin/phpcs --version
PHP_CodeSniffer version 2.2.0 (stable) by Squiz (http://www.squiz.net)

$ echo "" > foo.php
$ vendor/bin/phpcs --report=xml --standard=PSR2  < foo.php
ERROR: You must supply at least one file or directory to process.

Usage: phpcs [-nwlsaepvi] [-d key[=value]] [--colors] [--no-colors]
    [--report=<report>] [--report-file=<reportFile>] [--report-<report>=<reportFile>] ...
....

$ echo "" > test.php
$ phpcs --report=xml --standard=PSR2 < test.php
<?xml version="1.0" encoding="UTF-8"?>
<phpcs version="2.2.0">
<file name="STDIN" errors="0" warnings="1" fixable="0">
 <warning line="1" column="1" source="Internal.NoCodeFound" severity="5" fixable="0">No PHP code was found in this file and short open tags are not allowed by this install of PHP. This file may be using short open tags but PHP does not allow them.</warning>
</file>
</phpcs>
$ phpcs --version
PHP_CodeSniffer version 2.2.0 (stable) by Squiz (http://www.squiz.net)

$ php -v
PHP 5.6.4 (cli) (built: Jan 13 2015 15:11:56)